Category: Class 9

SCERT AP Board 9th Class Social Solutions 24th Lesson Traffic Education Textbook Questions and Answers.

AP State Syllabus 9th Class Social Studies Solutions 24th Traffic Education

9th Class Social Studies 24th Lesson Traffic Education Textbook Questions and Answers

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Question 1.
What documents should a driver carry while driving and what skills are needed to drive safely?
Answer:
The following documents should be carried while driving :

1. Driving license
2. Registration certificate
3. Taxation certificate
4. P.U.C. certificate
5. Insurance certificate
6. Fitness certificate and permit

The following is a basic description of the skills and abilities a driver needs before getting in the driver’s seat. This applies to people of all ages.

Physical skills and abilities :
Driving requires physical strength. It takes a lot of muscle work too.

1. Hold the body upright to use and control the steering wheel,
2. Maintain sitting balance,
3. Control the head, neck, arms and legs, feet and hands.
4. To operate a vehicle

Physical and mental stamina and muscle flexibility are needed to :

1. sit and drive
2. focus constantly on the task of driving.
3. twist and turn
4. move the head and’ neck side to side, up and down, back and forth.

In addition to these driving requires a clear and alert mind.

Question 2.
What will happen if someone jumps the traffic signal?
Answer:
Traffic signals help to control traffic. It someone jumps the traffic signal, there is a chance of accident.

Question 3.
Suggest a few steps that are taken in your area for road safety.
Answer:
Road safety is a result of contributing efforts from all the sections the society including both civilians and government officials. In addition to the human sufferings, the estimated costs of the road injuries are a noticeable amount in GNP per annum. So some steps can be fruitful in this direction.
A few important road safety steps :

1. Don’t use mobile phone whilst driving.
2. Belt up in the back.
3. Don’t drink and drive.
4. Always adhere to speed limits.
5. Take special care about children, senior citizens and pedestrians.
6. Don’t drive if tired.
7. Pedestrians should walk cautiously.
8. Always observe and anticipate other road users.
9. Keep your distance and
10. Always wear helmets and seat belts.

We follow all these road safety rules in our area.

Question 4.
Explain mandatory, caution and information traffic signs with examples.
Answer:
1) Mandatory signs :
Mandatory signs are indicated in a circular form. In accordance with the motor vehicle Act 1988, every driver of a motor vehicle shall drive the vehicle in conformity with any indication given by the mandatory signs and not obeying there signs is an offence.
Ex : 1. Stop
2. No Parking
3. Overtaking prohibited

2) Cautionary /Warning signs :
Cautionary signs are meant for cautioning the driver about the hazards lying ahead on the road. Drivers must obey there signs for safety. These signs are indicated in a triangular form
Ex : 1. T -inter section
2. Right hand curve
3. School ahead

3) Information signs:
Informatory signs are erected on the road to provide information on direction, destination, road side facilities etc., to the road users.
Ex : 1. Park this side
2. First aid post
3. Public telephone

Question 5.
Kamala wants to purchase a new vehicle. Explain her what are the steps to be taken and what documents are to be produced for the registration of a vehicle?
Answer:
The steps to be taken by Kamala in purchasing a car or something else :

1. Starting out
2. Using incentives and rebates
3. Pricing the car
4. Finding the exact car you want to buy
5. Test driving the car salesman
6. If you are trading in your old car
7. Negotiating for the best finance options
8. Closing the deal
9. Reviewing and signing the paper work,
10. Inspecting and taking possession of your new car.

Documents to be produced for the registration of a vehicle :

1. R.T.O. forms – a) Form 20 b) Form 34
2. Pan card , copy of sales certificate
3. Address proof
4. Insurance cover note
5. Person’s authorized signature
6. Copy of road worthiness certificate
7. Pollution under control certificate

Question 6.
Ramu wants to interchange his vehicle number to other vehicle. Is it correct or not?
Explain, why.
Answer:
No. Ramu cannot interchange his vehicle number to other vehicle.
Reason : Any vehicle registered for its particular registration mark will remain its
identifications and interchange of it is not allowed.

Question 7.
Explain the need of road safety.
Answer:
India loses more than 1,00,000 lives due to road traffic crashes every year. It has a road traffic fatality rate of 16.8 deaths per, 1,00,000 population. Approximately half of all deaths on the country’s roads are among vulnerable road users – motorcyclists, pedestrians and cyclists.

Hence road safety is very important to avoid the accidents and control loss of lives. Road safety ensures that every road user follow traffic rules and thereby avoid traffic jams and deaths due to accidents. For systematic regulation of vehicular traffic, road safety is needed.

Question 8.
Read the table of page ‘Accident Victims Age’ on page 286, identify the age group for which more number of cases registered and draw a bar graph.

Answer:
More number of cases registered age group 35 – 40 years age group.

Question 9.
Read the paras under the title ‘Traffic Chaos’ of page 287 and comment on them.
Traffic Chaos:
You have to go to school on the morning. If you are late, you may miss classes. You are struck in a traffic jam. What will you do?
Students, employees, labourers, teachers, doctors and all are affected by traffic jams. Foot paths (Side walks) are considered a boon for pedestrains. Sometimes motorists drive on these side walks also.

Stray animals, fruit and vegetable seller, private vehicles like cars, autorickshaws are parking at No Parking Zones are the main causes for traffic jams. As there is an increase in population and use of automobiles, there has been a rapid increase in the volume of traffic on roads. To avoid the accidents, one must know the prescribed rules and regulations.
Answer:

Road sense on Indian streets is often completely missing. The Indian traffic conditions are chaotic, the drivers are reckless, and the roads are poor repair conditions.

There is a pecking order for right of way – cows / buffaloes are at the top, trucks and buses are second, and dogs and pedestrians are at the bottom. Two wheelers are pretty low down. Pot holes and speed breaker bends are common and rarely marked. Pedestrians, . animals, bicycles, ox carts and tractors all use the roads.

Question 10.
Collect the data from the traffic police /RTA officials who are nearest to you.
Month : Place :
No. of cases booked :

Analyse the data and discuss in your classroom regarding traffic situations in your area.
Answer:
Month : September Place : Vijayawada
No. of cases booked : 1986

The above data is revealing us the negligence of the vehicle riders and road users. They are to be strictly punished.

9th Class Social Studies 24th Lesson Traffic Education InText Questions and Answers

Question 1.
Why is it compulsory to have a driving license? (Text Book Page No. 288)
Answer:
Yes, it is compulsory to have a driving license. As per Motor Vehicle Act 1988, a valid driving license is necessary to drive any motor vehicle on public roads.

Question 2.
Observe the given table and answer the questions. (Text Book Page No. 286)

1) In which group do you find more cases? Can you say, why.
Answer:
25 – 30. As the people in this age become more independent, they are exposed to risks.

2) How many cases are there in the age group of both 20 – 25 and 25 – 30?
Answer:
345; 380

Question 3.
Observe the following pie-chart and answer the following questions. (Text Book Page No. 287)
1) Discuss the data relating to the accidents – accused vehicles in your classroom.

Answer:
Group discussion in classroom

2) Which type of vehicles are accused of more accidents? Can say why?
Answeer:
Two wheelers. Because they are in more number.

3) What are Traffic Rules and regulations? Discuss in your classroom.
Answer:
Traffic rules and regulations of the road are both the laws and the informal rules that may have been developed to facilitate the orderly and timely flow of traffic.
Note : Students should discuss in the classroom.

Question 4.
With the help of your teacher collect the road surface markings from RTA/Traffic police and discuss the uses of various markings in the classroom. (Text Book Page No. 290)
Answer:
Uses of various markings :

1. Road surface markings are used on paved roadways to provide guidance and information to drivers and pedestrians.
2. These markings promote road safety.
3. These are used to supplement the message of road signs and other devices.

Note : Students should collect road surface markings and discuss in the classroom.

SCERT AP Board 9th Class Social Solutions 17th Lesson Colonialism in Latin America, Asia and Africa Textbook Questions and Answers.

AP State Syllabus 9th Class Social Studies Solutions 17th Colonialism in Latin America, Asia, and Africa

9th Class Social Studies 17th Lesson Colonialism in Latin America, Asia and Africa Textbook Questions and Answers

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Question 1.
Match the following :

Answer:

Question 2.
How is the word ‘discovery’ and ‘exploration’ used by Europeans? What did it mean to people who were already living in those geographical locations?
Answer:
Discovery:

• The word “discovery” means “finding something that we did not know about it before”.
• But in European concept “discovery” is to find faster and easier routes to countries like India, China etc., without passing through regions controlled by Italian traders.

Exploration :

• The step next to discovery is exploration.
• Exploration in European context means “Sending expedition to countries and finding out what resources were available.”
• Europeans explored the backward African and Asian countries for natural resources like, gold, silver, silk, porcelain etc.

Views of native people :

• But the Europeans did not explore these countries but exploited them.
• Virtually the Europeans enslaved them, plundered them, forced them to trade with them etc.
• In South America the natives were deprived of their land and were massacred and driven to interiors.

Question 3.
What role did trade play in the colonisation?
(OR)
“Trade played a major role in the colonisation.” Do you agree? Why?
Answer:
Yes. I agree with this statement.
Reasons:

• Trade played an important role in colonizations.
• Trading items include silk, porcelain, tea, etc., from China; cotton textiles, steel and spices from India; tin, petroleum, rubber, spices, etc., from Indonesia and natural resources from Africa.
• The Europeans had established trading centres in these countries.
• They demanded monopolistic trade relations for the benefit of the colonial powers.
• The European powers had bought these exotic goods and sold them in Europe and made high profits.
• The first Dutch expedition, for example, fetched about 400% profit on its investment.
• As much of 25% of the Dutch government budget came from these profits.
• The English people forced Indians to produce opium and sold that opium in China and earned heavy profits.
• Thus trade played an important role in colonization.

Question 4.
How did the lives of native people in different countries affect the colonisation? Write two ideas each in the context of – crops cultivated/religion/use of natural resources – for the three continents.
Answer:

• Most of the countries were self-sufficient before colonization.
• These colonies were impoverished during colonial powers.

Crops cultivated :

• They were cultivating food crops and the colonies in all three continents were forced to cultivate commercial crops.
• There were shortage of food items and famines and droughts were frequent.

Religion :

• In Asia people were Hindus, Muslims and Buddhists. In Indonesia Muslims were massacred and forced to convert into Roman Catholism.
• In other continents also the Catholic Church played important role in the governance of the colonies.

Use of natural resources :

• All the natural resources like gold, diamonds, silver, iron, coal, tin, rubber, silk, copper were plundered and taken into their countries.
• Colonial powers developed industries in their countries with these resources.

Question 5.
Compare the nature of colonial rule over China and India and Indonesia. What difference and similarities do you find between them?
Answer:

Question 6.
Locate the Portuguese, Dutch, British and French colonies in the world map and filled with different colours.
Answer:

Question 7.
If you were a citizen of Britain, could you support its colonisation? As an Indian citizen could you support or reject colonisation. Give a brief account of your views.
Answer:
Attitudes towards colonialism have varied greatly from time to time and from place to place. I think this is ever present truth that the strong dominate the weak.

If I were a citizen of Britian or as Indian I strongly oppose this colonisation. Because every living being in this world has the freedom in the world. So I don’t like to arrest the others’ freedom.

9th Class Social Studies 17th Lesson Colonialism in Latin America, Asia and Africa InText Questions and Answers

Question 1.
Which of the continents were they not familiar with at all? (Text Book Page No. 205)
Answer:
The Europeans were not familiar with the continents of South America and North America.

Question 2.
Which were the continents whose coastal areas were known to them but not the interior regions? (Text Book Page No. 205)
Answer:

• The coastal areas of Africa were known to the Europeans.
• They established trade relations with Asian countries during ancient and medieval periods. Hence the coastal areas of Asia were also known to them.

Question 3.
Why do you think the Spanish Settlers were not allowed positions of importance in the government of the colonies? (Text Book Page No. 208)
Answer:

• Even though the direct colonial rule ended, many remains of the old colonial rule remained.
• Latin Americas had a social system which consisted of very large landlords, a large number of slaves, semi slaves and poor small farmers.
• Industry and trade were under the control of the landlords.
• These landlords paid no interest in developing.
• Old colonialism continued to influence the Latin Americas even after the end of the colonial regime.

Question 4.
Compare the Zamindari system in the Nizam state and the haciendas of South America. What similarities and differences do you find between them? (Text Book Page No. 209)
Answer:

• Haciendas were estates of thousands of acres which contained silver and copper mines, agricultural lands and also factories. They were owned by landlords.
• “Zamindari System” was created by the government. Zamindars were appointed and they were made the owners of the lands. Original owners became tenants.
• Landlords used to employ peons or unfree Indians and African slaves to work on Haciendas.
• Tenents used to work on the lands in Zamindari system and taxes were collected by the Zamindars.

Question 5.
Why do you think the Latin American countries remained undeveloped despite getting independence from colonial rule? (Text Book Page No. 211)
Answer:
I think that the Latin American countries remained undeveloped despite getting independence form colonial rule due to the following reasons :

1. Poverty,
2. Corruption,
3. Lack of a manufacturing base,
4. Drugs,
5. Poor leadership and
6. The U.S.A.

Question 6.
In what way did the Munroe doctrine protect the independence of Latin America? Did it also limit their freedom? (Text Book Page No. 211)
Answer:

• The Munroe doctrine had no clarity regarding the independence of Latin America.
• It asserts that European powers should not consider colonising any American country but it allows an American country to colonize these countries.

Question 7.
How did Britain gain from the Munroe Doctrine? (Text Book Page No. 211)
Answer:

• Britain which had a powerful navy supported the Munroe Doctrine.
• Britain was keen that the American colonies were not under political control of any European power so that they would be free to trade with England and purchase its industrial goods.

Question 8.
Fill in the blanks : (Text Book Page No. 215)
a) Main products imported by western countries from China were ………………………….. and ………………………….. .
b) The product that western countries tried to sell in China was …………………………..
c) Asian country that tried to influence trade in China was …………………………..
Answer:
a) silk, porcelain and tea
b) opium
c) Japan

Question 9.
Read the following passage and answer the questions given below.

a) Why do you think the Italians were controlling the trade with Asia in 1400 and not other Europeans like Portuguese or Spanish? (Text Book Page No. 206)
Answer:

• As per theory the Italians came to an understanding with the Arab trader who brought Asian goods to the Alexandria and sold them to the Italians.
• But in reality Italy is in the Mediterranean sea and is very accessible to Egypt, Middle east and east Asian countries. Hence developed good trade with them.

b) Why were the Portuguese and Spanish keen to find other routes to reach Asia? (Text Book Page No. 206)
Answer:

• Italy developed due to the Asian trade.
• So other countries realised the importance of this trade.
• They wanted to find faster and easier routes to countries like India and China without passing through regions controlled by Italian traders.

Question 10.
Look at the map of South America around 1800 to identify the countries controlled by the different powers. (Text Book Page No. 202)

Answer:
Student activity.

Question 11.
Try to formulate the grievances of the following people of the Latin American colonies. (Text Book Page No. 209)
1) Spanish settlers who owned haciendas
2) Small Spanish farmers settled in America
3) Native Americans
4) African slaves settled in Latin America.
Answer:

1.  a) Haciendas were estates of thousands of acres.
   b) These estate owners had no intensives to use modern methods of cultivation or production as they had a supply of cheap abour.
2. Small Spanish farmers did not have any role in the administration of the colonies which were controlled by the Spanish from Europe.
3. A large number of native Americans had been killed. The survied were heavily taxed, and had to provide labour supply to the mines and farms owned by the Spanish.
4. Most of the African slaves were forced to work on the haciendas.

Question 12.
Look at the Map of Africa in 1913 to see the extent of colonial possessions of the European powers in Africa.
Compare the map with a modern map of Africa.
Make a list of the large African countries and write against their names the countries that had colonised them. (Text Book Page No. 216)

(OR)
Look at the two maps given beiow Map A shows the European colonies in Africa in 1913-14 and Map B shows the modern countries of Africa.

Compare the information in this two maps. Draw the table given below in yours answer sheet and write the name of the colonising country against the African Country given.
Answer:

AP State Syllabus AP Board 9th Class Physical Science Solutions Chapter 7 Reflection of Light at Curved Surfaces Textbook Questions and Answers.

AP State Syllabus 9th Class Physical Science Solutions 7th Lesson Reflection of Light at Curved Surfaces

9th Class Physical Science 7th Lesson Reflection of Light at Curved Surfaces Textbook Questions and Answers

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Question 1.
“Laws of reflection of light are not applicable to curved surfaces” Is it correct?
Answer:
No, laws of reflection of light are applicable to curved surfaces also.

Question 2.
How do you find the focal length of a concave mirror?
(OR)
What is the name given to distance between pole and focal point? How would you able to find that distance by using an activity? That distance is called focal length.
Answer:

To find the focal length of a concave mirror –

1. Hold a concave mirror perpendicular to the direction of sunlight.
   Take a small paper and slowly move it in front of the mirror and find out the point where you get smallest and brightest spot, which is image of the sun.
   The rays coming from sun parallel to the concave mirror are converging at a point.
   This point is called Focus or focal point (F) of the concave mirror.
   Measure the distance of the spot from the vertex (point P) of the mirror.
   This distance gives the focal length of the concave mirror.

Question 3.
Where will the image form when we place an object, on the principal axis of a concave mirror at a point between focus and centre of curvature?
Answer:

• When we place an object on the principal axis of a concave mirror at a point between focus and centre of curvature then the image will form at a point beyond the centre of curvature.
• The image is enlarged, inverted and real.

Question 4.
Find the distance of the image, when an object is placed on the principal axis at a distance of 10 cm in front of a concave mirror whose radius of curvature is 8 cm.
(OR)
If the object is placed on the principal axis at a distance of 10 cm in front of a concave mirror with curvature is 8 cm, what is the distance of the image?
Answer:
Object distance u = – 10 cm
Radius of curvature (R) = – 8 cm
∴ Focal length f = \(\frac{R}{2}=\frac{-8}{2}\) = – 4 cm
Image distance = v = ?

∴ The image distance = 6.67 cm.
i.e., Real image is formed at same side of the mirror.

Question 5.
State the differences between convex and concave mirrors.
(OR)
Distinguish between convex and concave mirrors.
(OR)
Ramu observed a mirror which is used by drivers to see the vehicles behind. Srinu observed a mirror which is used by dentist to see teeth inside the mouth. What are those two mirrors and distinguish them?
Answer:
Those mirrors are (1) Convex, (2) Concave

Question 6.
Distinguish between real and virtual images.
(OR)
Varun sees his image in a concave mirror. When he moves away he was unable to see his image. Write the differences between those two images.
Answer:

Question 7.
How do you get a virtual image using a concave mirror?
(OR)
Ramu moved an object towards a concave mirror. When he reached certain point he was able to see his image. Where does he had placed the object inorder to see the object in the mirror?
Answer:

• Place the object at a distance less than the focal length of the mirror.
• Draw ray diagram as shown in the figure.
• When the rays are extended, they seem to be coming out from a point on the other side of the mirror. (G)
• We cannot find the image on the screen, but we can see the image in the mirror. (IG)
• This is the virtual, erect and magnified image.

Question 8.
What do you know about the terms given below related to the spherical mirrors?
a) Pole
b) Centre of curvature
c) Focus
d) Radius of curvature
e) Focal length
f) Principal axis
g) Object distance
h) Image distance
i) Magnification
Answer:
a) Pole :
The centre of the spherical mirror is called pole of the mirror.

b) Centre of curvature :
The normal from a concave mirror converge at a point, that point is called centre of curvature.

c) Focus :
A point on the principal axis where a beam of light parallel to the principal axis either converges into or appears to diverge from after reflection from the mirror is called focus (or) focal point (F).

d) Radius of curvature :
The distance between pole and centre of curvature is called radius of curvature. It is denoted by ‘R’.
R = 2f

e) Focal length :
The distance of the focus from the pole is called the focal length (f) of the mirror.

f) Principal axis :
The horizontal line which passes through the centre of curvature and pole.

g) Object distance :
The distance between object and mirror is called object distance (u).

h) Image distance :
The distance between image and mirror is called image distance (v).

i) Magnification :
The ratio of size of image to the size of object is known as magnification.

Question 9.
Write the rules for sign convention.
(OR)
Vinay wants to solve a problem related to mirrors. What are rules to be followed by him in order to solve the problem?
Answer:

Sign conventions used in mirror equation :

1. All distances should be measured from the pole.
2. All distances measured in the direction of incident ray are to be taken as positive.
3. The distances measured in the direction opposite to incident ray are to be taken as negative.
4. Height of object (h₀) and height of image (h_i) are positive, if measured above principal axis and negative if measured below principal axis.

Question 10.
The magnification produced by a convex mirror is – 1. Do you agree it?
Answer:
The magnification produced by a convex mirror is – 1.1 agree with this statement.

Question 11.
Imagine that spherical mirrors were not known to human beings. Guess the consequences.
(OR)
What are the consequences occur when the spherical mirrors were not known to human beings?
Answer:

• Spherical mirrors are used by human beings in their daily life.
• Convex mirrors are used in hospitals, hotels, stores, apartments, roads, ATMs, computer monitors, rare-view mirrors in vehicles, and also in sun glasses,
• Whereas concave mirrors are used by ENT specialists, dentists to see inner parts of mouth,
• Car head lights are used to get parallel beam of light,
• Solar cookers are also made from concave mirrors, So everywhere we are using these spherical mirrors,
• So without these spherical mirrors the life of human beings is miserable,

Question 12.
By observing steel vessels and different images in them, Surya, a third class student, asked his elder sister Vidya some questions. What may be those questions?
(OR)
By observing the image on steel vessels, Surya asked his sister some questions. What may be those questions?
Answer:

• Why do we see our image in some vessels which bulged outwards?
• Why are we not able to see our image in some vessels which bulged inwards?
• Which type of vessels are useful to reflect light on wall and form our image on wall?
• Can we see the images in all vessels?
• Is these images real or virtual?
• The vessels which are bulged inside behaves like which type of mirrors?

Question 13.
How do you form a diminished image by a concave mirror on a screen?
Answer:
If we place an object beyond centre of curvature of a concave mirror, diminished image will be formed between focus and centre of curvature,

Question 14.
How do you find the focal length of a concave mirror in the lab?
Answer:
Aim :
To find out focal length of a concave mirror,

Material required :
A candle, paper, concave mirror, V-stand, measuring tape, or meter scale.

Procedure:
1) Place the concave mirror on V-stand, a candle, and meter scale as shown in figure.

2) Keep the candle at different distances from the mirror (10 cm to 80 cm) along the axis and by moving the paper (screen) find the position where you get the sharp image on paper.

3) Note the distance of candle from the mirror (u) and distance of the image from the mirror (v) in the given table.
Here u = object distance, v = image distance, f = focal length.

4) Find the average of T. This value of T is the focal length of the given concave mirror.

Question 15.
What do you infer from the experiment which you did with concave mirrors and measured the distance of object and distance of image?
Answer:
I observed the following points from the experiment with concave mirrors, to form images at different places, they are :

1. As the object distance increases, the image distance decreases.
2. As the object distance increases, the size of image decreases.

Question 16.
Draw a ray diagram to show the process of converging of the parallel beam by a concave mirror by taking four parallel incident rays.
Answer:

Question 17.
Draw suitable rays by which we can guess the position of the image formed by a concave mirror.
Answer:
Suitable rays by which we can guess the position of the image formed by a concave mirror.

Rule 1 :
All the rays, that are parallel to the axis, get reflected such that they pass through the focal point of the mirror.

Rule 2 :
A ray that passes through the focal point of the mirror will, travel parallel to the axis after reflection.

Rule 3 :
A ray, passing through the centre of curvature of the mirror and incidents on the mirror, after reflection will travel along the same line, but in opposition direction.

Question 18.
Show the formation of image with a ray diagram, when an object is placed on the •principal axis of a concave mirror away from the centre of curvature.
Answer:

Question 19.
Make a solar heater / cooker and explain the process of making.
(OR)
Which cooker uses solar energy to cook food and explain its making?
(OR)
Explain the construction and working of a solar cooker.
Answer:

Construction:

1. Make a wooden / iron frame in dish shape. It is solar cooker.
2. Cut the acrylic mirror sheets into 8 or 12 pieces in the shape of isosceles triangles with a height equal to the radius of a dish antenna.
3. The bases of 8 or 12 triangles together make the circumference of the dish.
4. Stick the triangle mirrors to the dish as shown in figure.
5. Thus solar heater/cooker is ready.

Working:

1. Face it towards the sun.
2. Find its focal point and place a vessel at that point.
3. It will get heated. Everyone cook rice in that vessel.

Question 20.
To form the image on the object itself, how should we place the object in front of a concave mirror? Explain with a ray diagram.
(OR)
Draw ray diagram to explain the image formation on the concave mirror if the object is in front of it.
Answer:

• The object should be placed on centre of curvature of concave mirror.
• When the object placed at centre of curva¬ture after reflection from the mirror the light rays converge at centre of curvature.
• So a real and inverted image is formed on the object itself. Ray diagram

Question 21.
How do you appreciate the role of spherical mirrors in our daily life?
(OR)
Write the usage of spherical mirror in daily life situations.
Answer:

• Spherical mirrors are useful in our daily life in many ways.
• Convex mirrors are used as rear view mirrors in cars, scooters, buses, etc. This helps us to see the traffic behind the vehicle, which avoids accidents while taking turns.
• Big convex mirrors are used as shop security mirrors.
• Concave mirrors are used by dentists, opthamologists, to see the smaller parts of teeth, eyes, and ears.
• Concave mirrors are also used in solar heating devices.
• Concave mirrors are used as shaving mirrors to see a large image of the chin (or) face.
• Concave mirrors are used as doctor’s head mirrors to focus light coming from a lamp on to the body parts of the patient to be examined by the doctor.
• So, I appreciate the role of spherical mirrors in our daily life.

Question 22.
How do doctors use concave mirrors?
Answer:

• Dentists and ENT specialist doctors use concave mirrors to get a magnified clearer view of the teeth, skin and ear cavities.
• A concave mirror converges the rays of light falling on it in a direction parallel to the principal axis, on to its focus. This is the reason why ENT specialists use it as a head mirror.

Question 23.
Why do we prefer a convex mirror as a rear-view mirror in the vehicles?
Answer:

• Convex mirror always gives an erect and diminished image.
• The image distance will be smaller than the object distance.
• A convex mirror has a wider field of view than a plane mirror.
• Hence we prefer convex mirror as rear-view mirror in the vehicles, as we have to observe the vehicles which are at the back of our vehicle.

Question 24.
Complete the table-1 which is related to experiment done by a concave mirror.

Answer:

From the given data, m = \(\frac{40 \mathrm{~cm}}{40 \mathrm{~cm}}\) cm = 1.
Hence, R = 40 cm, f = 20 cm.

Question 25.
How can you show the diverging and the converging of light by using laser lights?
Answer:
Aim :
To show diverging and converging of light by using laser lights.

Material required :
Concave mirror, convex mirror, laser lights-2, screen, V-stand, Agarbathi.

Procedure:

• Place a concave mirror on a V-stand and place the V-stand on a table.
• Take two laser lights.
• Focus the light rays of laser lights parallel to the axis of the concave mirror.
• The light rays (beams) incident on the concave mirror are reflected back and converge at one point.
• Place the screen to catch that converging point of reflected light rays.
• Light a Agarbathi near the table.

Observation :
We can observe path of the incident and reflected rays clearly in the smoke of Agarbathi.

• Now place a convex mirror on the stand.
• Again pass the laser light rays parallel to the principal axis at the convex mirror.

Observation :
We can observe diverging light rays. We cannot catch any converging point on the screen.

Question 26.
Collect information about the history of spherical mirrors in human civilization. Display it in your classroom.
Answer:

• The idea of mirror came into existence long back when people saw their images in water, on poluted surfaces, etc.
• The history of mirrors starts in the 6000 BC. The earliest man made mirrors were pieces of poluted stone.
• The first glass mirrors were produced in 1A.D. by Romans.
• The first modern silver-glass mirror was created by Justus Von Liebig, a German chemist in 1835.
• The invention of glass blowing method during the 14th century led to the discovery of spherical mirrors, which increased the popularity of glass mirrors.
• By the end of 18^th century, decorative mirrors have widely used.
• New, cheaper techniques of mirror production in the 19th century led to a great proliferation in their use.

Question 3.
Think about the objects which act as a concave or convex mirrors in your surroundings. Make a table and display it in your classroom.
(OR)
Collect some objects from your surroundings that act as concave, convex mirrors and display them your classroom.
Answer:
Object used as convex and concave mirror in our surroundings.

Question 4.
How will our image be in concave and convex mirrors? Collect photographs and display in your classroom.
Answer:

• In concave mirrors our image is thin and enlarged.
• As we move away from mirror the image will be diminished and become pointed at the pole.
• In convex mirror, our image is bulged and size of image is diminished.
• As we move away from the mirror, the image is further diminished.

Question 5.
How do you appreciate the use of reflection of light by a concave mirror in making of TV antenna dishes?
Answer:

• The parabolic shape of dish reflects the signals to the dish’s focal point.
• Mounted on brackets at the dish’s focal point is a device called a feed horn.
• This feed horn is a wave guide that gathers the signals at or near the focal point and conducts them to a LNB (Low-Noise Block down converter).
• The LNB converts these electromagnetic waves into electrical signals and shifts to the receiver i.e. T.V. set.
• This is all possible only with the help of parabolic dish antennas (concave shape).
• We know, the T.V. plays an important role in our daily life. So the inventions of the utilities of concave shapes are more helpful for us.

Question 6.
A convex mirror with a radius of curvature of 3 m is used as rear view in an automobile. If a bus is located at 5 m from this mirror, And the position, nature and size of the image.
Answer:

Position = 1.15 m behind the mirror. Nature = Virtual and erected.
∴ Image is erect and smaller in size by a factor of 0.23.

Question 7.
An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm. Find the position and nature of the image.
(OR)
An object 5 cm high is placed at a distance of 10 cm from a convex mirror, the focal length of the mirror is 15 cm. Find the nature, position and size of the image.
(v = +6m ; m = 0.6, h₂ = 3 cm)
Answer:
Given, u = – 10 cm ; f = 15 cm ; v =?

So the Image is virtual and seen in the mirror.
Magnification m = \(-\frac{v}{u}=\frac{-6}{-10}=\frac{6}{10}\) = 0.6
Position : 6 cm behind the mirror.
Nature : Virtual and erect image.
So the image is erect and diminished.

Question 8.
Write answers to the following questions based on the data given in the table – 3.
1) What changes will come gradually in the size of an image, when we move an object away from the concave mirror?
2) In which situation inverted images formed by a concave mirror?
3) If the centre of curvature of a concave mirror is 10 cm, where the object should be placed to get an image at centere of curvature?
Answer:
1) a) If we move an object from a concave mirror to its focus (F), we will get a virtual image.
b) If we place the object at ‘F, the size of the image is infinity.
c) If we move, the object from ‘F to centre of curvature the size of the image is decreases gradually but the size of the image is bigger than that of the size of the object.
d) At ‘C the size of the image is same as the size of the object.
e) From ‘C’ to infinity distance the size of the image is smaller than the siz4 of$he object and decreases gradually.
f) Hence, the size of the image decreases if we move an object away from the focus fo the concave mirror.

2) If we place an object beyond focus (F) inverted image will be formed.

3) At 10 cm distance (or) at u = 10 cm.

9th Class Physical Science 7th Lesson Reflection of Light at Curved Surfaces InText Questions and Answers

9th Class Physical Science Textbook Page No. 111

Question 1.
Did you burn a paper by using a magnifier?
Answer:
Yes.

Question 2.
What causes burning of the paper, while doing it?
Answer:
Converging light rays through magnifier at one point on the paper.

Question 3.
Can you use a plane mirror to burn a paper instead of a magnifier lens?
Answer:
Cannot.

Question 4.
Can’t? Why?
Answer:
Plane mirror cannot converge light rays.

Question 5.
Which type of mirrors may be used to converge light rays?
Answer:
Concave mirrors.

Question 6.
Which type of reflected surface used by Archimedes?
Answer:
Curved reflected surfaces.

9th Class Physical Science Textbook Page No. 112

Question 7.
Can we burn a paper by using light rays of the torch light?
Answer:
Cannot.

Question 8.
Can’t? Why?
Answer:
The light rays coming from the torch light are not parallel rays. Hence, they cannot converge at one point on the paper with high intensity.

Question 9.
Which type of incident rays are required to get high intensity and point sized converging point?
Answer:
Parallel light rays.

Question 10.
Which line is taken as a base to draw a reflected ray to the given incident ray?
Answer:
Normal taken as base.

9th Class Physical Science Textbook Page No. 114

Question 11.
Does a concave mirror from image at focus in all situations?
Answer:
No

9th Class Physical Science Textbook Page No. 114

Question 12.
See the given figure, a set of parallel rays are falling on a convex mirror. What conclusions can you draw from this?

Answer:
The parallel rays are diverging after reflection. If we extend the reflected rays backwards, they meet at F which is focal point of convex mirror. The image formed is virtual, straight and point sized.

Question 13.
Will you get a point image if you place a paper at the focal point?
Answer:
We can get highly enlarged image at infinity when we place paper at focal point.

9th Class Physical Science Textbook Page No. 118

Question 14.
How can you find the focal length of a convex mirror?
Answer:

• The focal length of a convex mirror can be determined by introducing a convex lens between the object and the convex mirror.
• An image can be obtained with the help of a convex lens side by side with object when the convex mirror reflects the rays along the same path.
• Then, the radius of curvature (R) of the mirror is the distance between the screen and the mirror.

• The focal length ‘f of the convex mirror is calculated using the formula R (Radius of curvature)
  

Question 15.
Can we get a magnified image by a convex mirror?
Answer:
No, convex mirror cannot form magnified image.

9th Class Physical Science Textbook Page No. 119

Question 16.
How can one see an image formed on the object itself?
Answer:
When an object placed at centre of curvature the image should form at C in inverted position. So the image formed on the object itself.

Question 17.
Do you get an image when object is placed at F? Draw a ray diagram. Do the experiment.
Answer:

When an object placed at F, we can get the image at an infinite distance.

9th Class Physical Science 7th Lesson Reflection of Light at Curved Surfaces Activities

Activity – 1

1. Observation the light rays on concave and convex surfaces.
Answer:
Procedure :

1. Take a rectangular shaped (3″ x 6″) Acrylic sheet.
2. Hold the Acrylic sheet with your palm without bending it.
3. Ask your friend to focus light with a torch light on the sheet.
4. Now adjust the sheet as reflected rays are caught on a wall.
5. Now bend slowly your palm as the sheet bends inwards in the shape of concave.
6. Again ask your friend to focus the light.
7. Now bend slowly your palm as the sheet bends outwards in the shape of convex.
8. Again ask your friend to focus the light.

Observation :

1. In the first case, when without bending the sheet, reflected light is not converged at one place. Because the sheet was acted as a plane mirror.
2. In the second case, reflected light converged at one place. Because the acrylic sheet is bent inwards and it is acted as a concave mirror.
3. In the third case, reflected light rays are not converged, of course they diverged with low intensity. Because the sheet was acted as a convex mirror.

Conclusion :
Concave surfaces converge light rays and convex surfaces diverge.

Activity – 2

Question 2.
Show that a powerful source far away is needed to get parallel rays of light.
Answer:

1. Stick two pins on a thermocole block.
2. The pins are exactly parallel to each other.
3. When a source of light is kept very near, we see the shadows diverging (from the base of the pins).
4. As we move the source away from the pins, the angle of divergence gets reduced.
5. If we move the source far away we will get parallel shadows. But the light intensity reduces.
6. That means to get a beam of parallel rays all that we need is a powerful source far away.

Activity – 3

Question 3.
Identify the focus or focal point of concave mirror.
(OR)
How do you able to find the focal point of a given concave mirror? Explain it with an activity.
Answer:

1. Hold a concave mirror perpendicular to the direction of sunlight.
2. Take a small paper and slowly move it in front of the mirror and find out the point where we get smallest and brightest spot image of the sun.
3. The rays coming from the sun parallel to the concave mirror are converging at a point.
4. This point is called Focus or focal point (F) of the concave mirror.

Activity – 4

Question 4.
Find the normal to a curved surface.
(OR)
How do you find normal to a curved surface ? What is the name given to wavering point of normals, explain.
Answer:

• Take a small piece of thin foam or rubber (like the sole of a slipper).
• Put some pins in a straight line on the foam.
• All these pins are perpendicular to the plane of foam.
• If the foam is considered as a mirror, each pin would represent the normal at that point.
• Any ray incident at the point where the pin makes contact with the surface will reflect at the same angle as the incident ray made with the pin-normal.
• If we bend the foam piece inwards, we will notice that all the pins tend to converge at a point.
• If we bend the foam piece outwards, the pins seem to move away from each other or they diverge.
• This gives us an idea about spherical mirror.
• A concave mirror will be like the rubber sole bent inwards (fig. b) and the convex mirror will be like the rubber sole bent outwards (fig. c).

• For a concave mirror, like these pins all normals will converge towards a point. This point is called centre of curvature (C) of the mirror.
• For the ray R, the incident angle is the angle it makes with the radius (normal) shown as Zi and the reflected angle is shown as Zr. We know by first law of reflection Zi = Zr.

Lab Activity

Question 5.
Write the experimented method in measure the distances of object and image using concave mirror. And write the table for observations.
(OR)
Write an experimental activity which gives the information about types of images and measuring the object distance and image distance.
Answer:
Aim :
Observing the types of images formed by a concave mirror and measuring the object distance and image distance.

Material required :
A candle, paper, concave mirror, V-stand, measuring tape or meter scale.

Procedure:

1) Place the concave mirror on V-stand, a candle and meter scale as shown in figure.
2) Keep the candle at different distances from the mirror (10 cm to 80 cm) along the axis and by moving the paper find the position where we get sharp image on paper.

3) Note down the observations in table -1

4) Since we know the focal point and centre of curvature, we can re-classify the above observations as shown in the table – 2.

5) Then note down the observations in table – 2

AP State Syllabus AP Board 9th Class Physical Science Important Questions Chapter 4 Atoms and Molecules

AP State Syllabus 9th Class Physical Science Important Questions 4th Lesson Atoms and Molecules

9th Class Physical Science 4th Lesson Atoms and Molecules 1 Mark Important Questions and Answers

Question 1.
What is the difference between 2N and N₂?
Answer:
2N means two nitrogen atoms.
N₂ means one nitrogen molecule.

Question 2.
Mohan said, “O₂ differs from O,”. Do you agree? Justify.
Answer:
1) Yes, I agree with Mohan’s statement.
2) ‘O’ means single oxygen atom.
‘O₂‘ means single oxygen molecule.

Question 3.
The atomic number (Z) of an element is 6. Name the element.
Answer:
Carbon.

Question 4.
Write any one precaution in doing the experiment chromotography.
Answer:
Make sure that the ink line or mark does not touch the water.

Question 5.
In a class, a teacher asked students to write the molecular formula of Oxygen, Namitha wrote the formula as “O₂“, Raju as “O”. Which one is correct?
Answer:
Namitha is correct.
Molecular formula of oxygen is O₂.

9th Class Physical Science 4th Lesson Atoms and Molecules 2 Marks Important Questions and Answers

Question 1.
Fill the following table.

Answer:

Question 2.
Compare the subatomic particles electron, proton and neutron.
Answer:

Question 3.
What are the materials used in “Conservation of mass” experiment?
Answer:
Material required for Conservation of mass:
Sodium sulphate, Barium chloride, distilled water, conical flask, spring balance, small test tube, rubber cork, thread, retort stand.

9th Class Physical Science 4th Lesson Atoms and Molecules 4 Marks Important Questions and Answers

Question 1.
Fill in the blanks in the table using the given information.

Answer:

Question 2.
Read the following information and answer.
Molecular mass of a molecule is the sum of the atomic masses of individual atoms in it.

i) Find the molecular mass of Na₂CO₃.
Answer:
Molecular mass of Na₂CO₃ = (23 × 2) + 12 + (16 × 3) = 46 + 12 + 48 = 106

ii) If the molecular weight of a compound is 44. Which is made with carbon and oxygen. What its molecular formula?
Answer:
Molecular weight of a compound = 44
At. mass of Carbon = 12 Remaining at. mass = 44-12 = 32 = 16 × 2
Hence, 16 × 2 ⇒ (Oxygen atomic mass × 2) ⇒ O₂
Molecular formula = CO₂

iii) What is the unit of atomic mass?
Answer:
Unit of atomic mass = amu
atomic mass unit (amu) is defined as precisely \(\frac{1}{12}\) the mass of an atom of carbon -12.

iv) On the basis of molecular weights of NaOH and H₂O, which is heavier?
Answer:
Molecular weight of NaOH = 23+16 + 1= 40
Molecular weight of H₂O = (1 × 2)+ 16 = 2 + 16=18
Hence, NaOH is heavier than H₂O.

Question 3.
Complete the table.

Answer:

9th Class Physical Science 4th Lesson Atoms and Molecules Important Questions and Answers

9th Class Physical Science 4th Lesson Atoms and Molecules 1 Mark Important Questions and Answers

Question 1.
How did the element Helium get its name?
Answer:
Place of discovery of element can also play a role in its naming. The gas which was first discovered in the sun was named Helium. Because, Greek name for sun is helios’.

Question 2.
What is an atom?
Answer:
An atom is the smallest particle of an element that can participate in chemical reaction and retain all its properties.

Question 3.
Is ‘Na’ an element or compound? Why?
Answer:
‘Na’ is an element, because it was formed by the same atoms of ‘Na’.

Question 4.
Is O₂ an element or compound? Why?
Answer:
O₂ is a compound, because O₂ is formed by combining two oxygen atoms.

Question 5.
What is an Avogadro number? What is its value?
Answer:
The number of particles present in one mole of any substance is the Avogadro number (N_A).
This is equal to 6.022 × 10²³.

Question 6.
Which instrument is used to calculate the atomic mass exactly?
Answer:
Mass spectrometer.

Question 7.
What is atomic mass?
Answer:
The number of times one atom of given element is heavier than 1/12th part of atomic mass of carbon -12 is called its atomic mass.

Question 8.
How molecules are formed?
Answer:
A molecule is formed by the combination of different kinds of atoms that are chemically bonded together by attractive forces.

Question 9.
Why is it not possible to see an atom with naked eye?
Answer:
The size of an atom is so small i.e., less than 1 nm (1 nano metre). So we are unable to see an atom.

Question 10.
What is a chemical formula?
Answer:
The chemical formula of a compound is a symbolic representation of its composition.

Question 11.
How many atoms are present in.
i) H₂S molecule and
ii) PO₄^3- ion?
Answer:
i) The number of atoms in H₂S molecule = 2 + 1=3
ii) The number of atoms in PO₄^3- ion =1 + 4 = 5

9th Class Physical Science 4th Lesson Atoms and Molecules 2 Marks Important Questions and Answers

Question 1.
Who is called as the father of modern chemistry? What are his main contributions?
Answer:

1. Antoine Lavoisier a French scientist is called as “Father of modern chemistry”.
2. He made many important contributions to chemistry.
3. One of his contributions is law of conservation of mass.

Question 2.
State the following.
a) Law of conservation of mass
b) Law of constant proportions
Answer:
a) Law of conservation of mass :
Matter is neither created nor destroyed during a chemical reaction.
(or)
The mass of the reactants is equal to the mass of the products of chemical reaction.

b) Law of constant proportions :
A given chemical substance always contains the same elements combined in a fixed proportions by weight.

Question 3.
What are the Dalton’s proposals about the nature of matter?
Answer:
John Dalton proposed the basic theory about the nature of matter. His proposals are :

1. If mass was to be conserved, then all elements must be made up of extremely small particles called atoms.
2. If law of constant proportions is to be followed, the particles of same substance couldn’t be dissimilar.

Question 4.
What is the proposal of Indian sage Kanada, about atom?
Answer:

1. About 2600 years ago, an Indian sage called Kanada, postulated atoms in his Vaishesika sutra”.
2. He proposed that all forms of matter are composed of very small particles known as “Anu”.
3. Each “Anu” may be made up of still smaller particles called “Paramanu”.

Question 5.
What is the use of symbols for elements?
Answer:

1. We know that chemistry involves a lot of reactions.
2. It will be a waste of time to write the full name of the elements and compounds every time to describe a reaction.
3. To avoid this we use symbols for naming the elements and formulae to represent compounds.

Question 6.
What are the characteristics of a symbol?
Answer:
1) A symbol can have either one or two letters of English.
Ex : H, He, N, Ne, etc.

2) The first letter of the symbol is always upper case and the second letter is always lower case.
Ex :
1) Al, Cr, Cl, etc. is the right method to represent elements.
2) CL, bE, he, etc. is the wrong method to represent elements.

Question 7.
In a reaction, 5.3 g of sodium carbonate reacted with 6 g of ethanoic acid. The products were 2.2 g of carbon dioxide, 0.9 g of water, and 8.2 g of sodium ethanoate. Show that these observations are in agreement with law of conservation of mass.
Answer:
Sodium carbonate + Ethanoic acid → Sodium ethanoate + Carbon dioxide + Water
The total mass of reactants = 5.3 + 6 = 11.3 g
The total mass of products = 2.2 + 0.9 + 8.2 = 11.3 g
∴ Total mass of reactants = Total mass of products
So these observations are in agreement with law of conservation of mass.

Question 8.
Hydrogen and oxygen combine in the ratio of 1 : 8 by mass to form water. What mass of oxygen gas would be required to react completely with 3 g of hydrogen gas?
Answer:
According to data 1 g of hydrogen is reacting with 8 g of oxygen.
So amount of oxygen would be required to react completely with 3 g of hydrogen
= 3 x 8 = 24 g

Question 9.
Calculate formula unit weight of ZnO, Na₂O, K₂CO₃ (Given atomic weight of Zn = 654)
Answer:
Formula unit weight of ZnO = 65 + 16 = 81 u
Formula unit weight of Na₂O = 2 × 23 +16 = 62u
Formula unit weight of K₂CO₃ = 2 × 39 + 12 + 3 × 16 = 138 u

Question 10.
Calculate the number of moles for the following.
i) 52 g of He (finding mole from mass).
ii) 12.044 × 10₂₃ number of He atoms (finding mole from number of particles).
Answer:

Question 11.
If one mole of carbon atom weighs 12 g. What is the mass of 1 atom of carbon?
Answer:

Question 12.
When 3 g of carbon is burnt in 8 g of oxygen 11 g of carbon dioxide is produced. What mass of carbon dioxide is formed when 3 g of carbon is burnt in 50 g of oxygen.
Answer:
3 g of carbon react with 8 g of oxygen to form 11 g of carbon dioxide.
Ratio of carbon and oxygen = 3 : 8
The amount oxygen react with 3g of carbon = 3 × 8 = 24.
So the amount of carbon dioxide formed = 3 + 24 = 27 g.

Question 13.
Given the names of the elements present in the following compounds.
a) Quick lime
b) Hydrogen bromide
c) Baking soda
d) Potassium sulphate
Answer:

Question 14.
Calculate number of sulphur (Sg) present in 16 g of solid sulphur.
Answer:
Molecular weight of sulphur = 8 × 32 = 256 g.
256 g of sulphur contains 6.022 × 10₂₃ molecules.
Number of molecules present in 16 g of sulphur = \(\frac{16}{256}\) × 6.022 × 10²³
= 3.77 × 10²² molecules

Question 15.
Anitha wrote the formula for oxygen molecule as 20. Is it correct or not? Why?
Answer:

1. It is not correct.
2. The formula of oxygen molecule is O₂.
3. 2O shows two separate atoms of oxygen.
4. O₂ shows molecule of oxygen.

9th Class Physical Science 4th Lesson Atoms and Molecules 4 Marks Important Questions and Answers

Question 1.
How elements got their names? Explain with examples.
Answer:
I: Sometimes elements are named based on their property.
Ex :
1) The Latin name for water is “hydro”.
So the element that combined with oxygen to give water was named as ‘hydrogen’.

2) The Latin word for acid is ‘oxy’.
Hence the gas that forms acid is ‘oxygen’.

II. Place of discovery of element can also play a role in its naming.
Ex : The gas that was first discovered in the sun (Greek name for the sun is “helios”) was named as ‘helium’.

III. Sometimes the elements were named to honour the scientists.
Ex : Einsteinium, Fermium, Rutherfordium and Mendelevium, etc.

Question 2.
Define the following terms.
a) Atomicity
b) Valency
c) Ions
Answer:
a) Atomicity :
The number of atoms constituting a molecule is known as its atomicity.

Ex :
1) Na is monoatomic
2) O₂ is diatomic
3) O₃ is triatomic

b) Valency :
Atoms of the elements have power to combine with atoms of other elements. This is known as valency.
Ex :
1) Valency of carbon is 4.
2) Valency of oxygen is 2.
3) Valency of hydrogen is 1.

c) Ions:
1) Ions may be a single charged atoms or a group of atoms that have a net charge on them.
2) A negatively charged ion is called anion and the positive charge ion is cation.
Ex : Na⁺, Cu⁺², S^2-, N^3-, etc.

Question 3.
Explain the method of writing a formula to a compound using criss – cross method, with the help of an example.
Answer:
The following steps should be taken while attempting to write a chemical formula using criss – cross method.
Ex : Take sodium carbonate as an example.
1) Write the symbols of atoms or group of atoms side by side, usually the cation first.
NaCO₃

2) Write the valency of each atom or group of atoms on the top of its symbol.
Na¹ (CO₃)²

3) Divide the valency number by their highest common factor if any to get the simple ratio.
Na¹ (CO₃)²

4) Interchange the valency and write the numbers to the lower right of the constituents as subscript.
Na₂(CO₃)₁

5) If any constituent receives the number 1, ignore it while writing the formula.
Na₂CO₃

6) If group of atoms received the number more than 1, enclose it within brackets. Hence the formula for the sodium carbonate is Na₂CO₃.

Question 4.
Define the terms :
a) molecular mass,
b) formula unit mass,
c) mole and
d) molar mass.
Answer:
a) Molecular mass :
The molecular mass of a substance is the sum of the atomic masses of all the atoms in a molecule of a substance.

b) Formula unit mass :
The formula unit mass of a substance is a sum of the atomic masses of all atoms in a formula unit of a compound.

c) Mole :
1) One mole of a substance is the amount of the substance which contains as many particles or entities that are equal to the atoms present in exactly 12 grams of C¹² isotope.
2) The number of particles present in one mole of any substance has a fixed value of 6.022 × 10²³. This number is called Avogadro’s constant (N_A).

d) Molar mass :
The mass of 1 mole of a substance which is expressed in grams is called its molar mass.

Question 5.
What are the main postulates of Dalton’s atomic theory?
Answer:
The main postulates of Dalton’s atomic theory are :

1. Matter consists of indivisible particles called atoms.
2. Atoms are neither created nor destroyed in a chemical reaction, but atoms will reorganize.
3. All the atoms of a given element have identical mass and chemical properties.
4. Atoms of different elements have different masses and chemical properties.
5. Compounds are formed when atoms of different elements combine in simple whole number ratios i.e., chemical change is the union or separation of atoms as a whole number.

Question 6.
Draw the pie diagram to understand the atomic mass and explain it.
Answer:

Explanation :

1. Let us assume the circle in the diagram represents mass of one carbon – 12.
2. It is divided into 12 equal parts as shown in the figure.
3. Each part represents 1/12th of atomic mass of one carbon -12.

Atomic mass unit :
One atomic mass unit is defined as the mass exactly one-twelfth the atomic mass of carbon – 12 isotope.

Question 7.
Illustrate the concept of mole through a diagram.
Answer:
Mole :

1. One mole of a substance is the amount of the substance which contains as many particles (atoms, molecules etc.) or entities that are equal to the atoms present in exactly 12 grams of ¹²C isotope.
2. The number of particles present in one mole of any substance has a fixed value of 6.022 × 10²³. This number is called Avogadro’s constant (N_A).

Question 8.
How can you appreciate John Dalton for proposing his atomic theory?
Answer:

• We know, development of science and technology is a combined effort of Roman scientists.
• The zeal to know or discover something new, leads the scientists for their discoveries.
• One of such is the atomic theory proposed by Dalton, based on Lavoisier’s law of conservation of mass and Proust’s law of constant proportions.
• Dalton said atom is indivisible.
• This proposal lead to discover many new things by various scientists and to unveil the complete structure of atom.
• Hence Dalton’s contribution is highly appreciable.

Question 9.
How do you feel after studying the symbols and formulae of different elements and compounds?
Answer:

• In my earlier class I came to know that chemistry is nowhere but in our kitchen.
• I used to call so many chemicals with their names.
• Now I am able to call them with their symbols and formulae.
• For example 1 can call the common salt as NaCl.
• This thrills me alot, and I am curious to know the formulae of so many common household substances.
• This is very helpful for my higher studies.

Question 10.
Describe the experiment conducted by Joseph L. Proust, which lead him to propose law of constant proportions.
Answer:

• Proust took two samples of copper carbonate, one from nature and another prepared in the lab.
• These two samples are chemically decomposed to find percentage of copper, carbon and oxygen.
• The results obtained are given in the table.

• From the above table we observe that the percentage of copper, carbon and oxygen atoms in two samples are same.
• Based on this observation Proust proposed the law of constant proportions as “A given chemical substance always contains the same elements combined in a fixed proportions by weight”.

Question 11.
Write down the formulae of these compounds, using criss – cross method?
i) Sodium oxide
ii) Aluminium chloride
iii) Sodium sulphate
iv) Magnesium hydroxide
Answer:

Question 12.
Write down the names of compounds represented by the following formulae and also write the anion, cation.
i) Al₂(SO₄)₃
ii) CaCl₂
iii) K₂SO₄
iv) KNO₃
v) CaCO₃
Answer:

Question 13.
What are the rules you have to follow while writing a chemical formula?
Answer:

1. The valencies or charges on the ion must balance.
2. When a compound consists of metal and non-metal, the name of the symbol of metal is written first, eg : Calcium oxide (CaO)
3. In compounds formed with poly atomic ions, the ion is enclosed in a bracket before writing the number to indicate the ratio.

Question 14.
Calculate the molecular weight H₂, O₂, Cl₂, CO₂, CH₄, C₂H₆, C₂H₄, NH₃, CH₃OH.
Answer:
Molecular weight of H₂ = 2 × 1 = 2 u
Molecular weight of O₂ = 2 × 16 = 32 u
Molecular weight of Cl₂ = 2 × 35.5 = 71 U
Molecular weight of CO₂ = 12 + 2 × 16 = 44 u
Molecular weight of CH₄ = 12 + 4 × 1 = 16 u
Molecular weight of C₂H₆ = 2 × 12 + 6 × 1= 30 u
Molecular weight of C₂H₄ = 2 × 12 + 4 × 1= 28 u
Molecular weight of NH₃ = 14 + 3 × 1 = 17 u
Molecular weight of CH₃OH = 12 + 4 × 1 + 16 = 32 u

Question 15.
a) What is atomicity?
b) Give examples.
c) Why do elements have different atomicities?
Answer:
a) Atomicity:
The number of atoms constituting a molecule is known as its ‘atomicity’.

b) Examples :
A molecule of hydrogen consists of two atoms of hydrogen. Here the atomocity is two. Hence it is known as a diatomic molecule. Helium (He), Argon (Ar) exist as single atom. Hence they are known as monoatomic.
Ozone (O₃) has tetratomic
Sulphur (S₈) has octatomic

c) Every element has a definite combining capacity, that determines the atomicity of its molecules. Every element reacts with other element according to its combining capacity, which we call as its valency.

SCERT AP Board 9th Class Social Solutions 23rd Lesson Disaster Management Textbook Questions and Answers.

AP State Syllabus 9th Class Social Studies Solutions 23rd Disaster Management

9th Class Social Studies 23rd Lesson Disaster Management Textbook Questions and Answers

Improve Your Learning

Question 1.
Explain how a natural hazard becomes a disaster.
Answer:

• A natural hazard is a natural event of unusual magnitude that people don’t expect and cannot control.
• Natural hazards threaten people’s lives and their activities and can forever change their ways of living.
• A natural hazard event can become a natural disaster when causes the destruction of people’s property or their injury and/or death.

Question 2.
What is Terrorism? What are the motives of terrorists?
Answer:
A common definition of terrorism is the systematic use or threatened use of violence to intimidate a population or government and thereby effect political, religious or ideological change.
Motives of terrorism :

• Terrorism is a type of violence used tactically in peace, conflict and war.
• The motivation of terrorists are quiet various depending on what they hope to accomplish.
• The majority of the motives can be broken down into three broad areas: rational, psychological and cultural.
• Although some motives are difficult for the majority of the world to comprehend given a motive, a terrorist group has a purpose for violence.

Question 3.
What safety measures should be followed to avoid fire accidents?
Answer:
Safety measures to be followed to avoid fire accidents:

• Prevention of fire is necessary for avoiding accidents.
• Never leave the kitchen during cooking, no matter what the circumstance.
• All the inflammable things or liquids should not be kept near the fire.
• Electrical appliances should have incorporated in an automatic cut off feature for some time. Timers can be used for these.
• Wear suitable dresses while cooking.
• Installation of fire detectors in the house will alert automatically the fire department.
• One should not smoke in bed/throw burning buds here and there.
• One should not play crackers etc., near the house.
• One should not keep match boxes, lighter etc., at the reach of the children.
• One should not keep agarbattis carelessly.
• One should not make fire when wind is blowing.
• One should close the regulator of the gas cylinder properly etc.

Question 4.
What are the main causes of road accidents? How can we reduce the road accidents?
Answer:
The main causes of road accidents:

1. Alcohol & drunk – driving.
2. Speeding
3. Weather related
4. Hydroplanning
5. Animals in road.
6. Street racing.
7. Cell phones.
8. Music, CD players, Radio distractions
9. Driver fatigue
10. Suicide car accidents.

Steps to reduce road accidents :

1. Strict enforcement of speed limits.
2. Heavy penalty should be imposed on all those who cross speed limits.
3. Lower age limit for 2 wheeler and heavy vehicle licence should be raised to 21.
4. Driving tests for issue of driving license is to be made more stringent and fool proof.
5. Helmet should be made compulsory by law.
6. Existing traffic rules should be strictly enforced, etc.

Question 5.
Terrorist attacks cause loss of life and wealth. What are the precautions to be taken to prevent these activities?
Answer:

• Devastating acts have left many concerned about the possibility of future incidents.
• Taking preparatory action can reassure us that we can exert a measure of control even in the face of such events.
• Finding out what can happen is the first step. Then develop a disaster plan.
• Create an emergency communications plan.
• Establish a meeting place.
• Assemble a disaster supplies kit.
• If disaster strikes :
  a) Remain calm and be patient.
  b) Follow the instructions of local emergency officials.
  c) If the disaster occurs near you, check for injuries. Give first aid and get help for seriously injured people.

Thus we can protect from terrorist attacks.

Question 6.
Identify the causes of rail accidents.
Answer:
Causes of rail accidents :

1. Lack of proper maintenance.
2. Human error or sabotage.

Question 7.
List out the reasons and risk inducing factors in your home, school or village.
Answer:
Three risk inducing factors :

1. In my home: Nothing.
2. In my school:
   a. There is a big pit in our school. I think it is dangerous.
   b. We have 3 storeyed building as our school. The little children are in the third stair. I think it is also a risk factor.
3. In my village : My village is in earthquake zone.

Question 8.
Locate the following places attacked by terrorists in the India map.
a) Mumbai
b) Hyderabad
c) Bhagalpur
d) Kumbakonam
e) Bengaluru
Answer:

Question 9.
Write about an incident related disaster you know.
Answer:
Some years ago we went to Marina beach in Chennai. We enjoyed a lot by playing there. We built some structures in the sand. We ate peanuts, groundnuts, mango pieces, etc. on our return we walked far away from the sea. Suddenly we heard the noises of the people in the beach. Then we saw a big wave. Many were drowned and lost their lives. We ran very fast from the place. By god’s grace we are still alive.

Question 10.
Read the para under the title ‘Fire Accidents’ on page 281 and comment on it.
Fire Accidents :
The 2004 fire in a school in Kumbakonam, Tamilnadu sparked ofT debates and arguments on the safety of schools in the*ountry. 93 innocent people were charred to death. The main causes of this fire were lack of awareness amongst children and teachers as to what to do in case of a fire, lack of preparedness, kitchen close to the classroom etc. However, incidents like these are not new.
Answer:
Fire accidents can be due to various reasons. They include open flames such as a candle being accidentally being knocked over or through electrical faults. It is important to know the fire safety rules because fire accidents can result in disastrous personal injury and distressing damage. Fire safety plans are to be planned.

Question 11.
Collect information from newspapers and magazines about the human induced disaster that have taken place in the past few years in your state. Find out, what measures are being taken in your area to reduce such risks in the future.
Answer:
Nowadays road accidents became a common scenario in India. The main reasons behind the road accidents are not obeying speed limits, poor roads, drinking and driving, rash driving, aggressive driving etc.

Information about road accidents in Telangana and Andhra Pradesh :

On an average of last 6 years the number of accidents are 44,446 and the number of deaths are 14,882 in Telangana and Andhra Pradesh.
The following measures are taken to control the road accidents in Andhra Pradesh :

1. Increased traffic fines in India.
2. Suspending licence for drunken drivers.
3. Established traffic courts.
4. Started traffic awareness programmes for drivers.

Question 12.
List the various losses incurred due to terrorism.
Answer:

1. Fear in people
2. Psychological problems in people
3. Negative effect on tourism
4. Financial or economic losses
5. Unstable governments and
6. Loss of human lives, etc.

9th Class Social Studies 23rd Lesson Disaster Management Activities

Question 1.
From the nearest fire station, find out what are the other simple Do’s and Don’ts that you can follow and awareness to reduce fire accidents.
Answer:
I live in Vijayawada. We have fire station in Krishnalanka. I visited that and learnt the following. Do’s :

• Do have an adult always present when cooking is going on the kitchen. Children should not be allowed alone.
  Do keep hair tied back and do not wear synthetic clothes when you are cooking.
  Do make sure that the curtains on the window near the stove are tied back and will not blow on the flame or burner.
  Do check to make sure that the gas burner is turned off immediately if the fire is not ignited and also switched off immediately after cooking.
  Do keep matches out of the reach of children, etc.

Don’ts :

• Don’t put any clothes near the stove.
• Don’t wear loose fitting clothes or chunnies, etc.
• Don’t store spray cans or cans carrying inflammable items near the stove.
• Don’t let small children near an open oven door.
• Don’t lean against the stove to keep warm, etc.

Question 2.
Identify recent terrorist acts that have taken place in India, and discuss the possible effects of these acts on children.
Answer:
Terrorist attack at Amarnath on July 11, 2017 is recent attack that have taken place in India.

Many children are exposed to trauma and life-threatening solution, duringthe last few decades, thousands of children have been exposed to terrorism. The attacks significantly, affect the mental health of the children. Terrorist attacks and their aftermath have had a powerful impact on children and their families. Media and television exposure of terrorist events throughout the world has increased during the past few years. There is increasing concern about the effects of this exposure on children who witness these violent images. Recent studies have examined the effect of remote exposure of terrorist attacks and have shown a significant clinical impact on children and families.

AP State Syllabus AP Board 9th Class Physical Science Important Questions Chapter 5 What is inside the Atom?

AP State Syllabus 9th Class Physical Science Important Questions 5th Lesson What is inside the Atom?

9th Class Physical Science 5th Lesson What is inside the Atom? 1 Mark Important Questions and Answers

Question 1.
Write any two limitations of Rutherford’s atomic model.
Answer:

• The revolving electron would lose energy continuously and get directed towards positively charged nucleus and eventually crash into the nucleus.
• If this is true, the atoms would become highly unstable and the matter would not exist, but matter exists.

Question 2.
In Rutherford’s experiment, when the alpha particles hit the foil, Rutherford expected that all the alpha particles would be deflected by small angles. Why did Rutherford expect the above observation?
Answer:
Rutherford thought that positive charge is distributed throughout the atom.

Question 3.
Write an application of isotopes in the field of medicine.
Answer:

• The isotope of iodine is used in the treatment of goitre.
• The istope of cobalt is used in the treatment of cancer.

9th Class Physical Science 5th Lesson What is inside the Atom? 2 Marks Important Questions and Answers

Question 1.
What is valency? Write valency of hydrogen.
Answer:

• The number of electrons present in outer most orbit of an atom is called its valency.
• Valency of hydrogen is 1.

Question 2.
Observe the table given below.

Answer the following questions.
i) Which Shell has highest number of electrons?
ii) Write the general form of the formula to find maximum number of electrons in each shell?
Answer:
i) 0 Shell ‘N’.
ii) 2n² (n = 1, 2, 3, ……..)

Question 3.
Convert 36g of water into mole?
Answer:
Water molecular formula = H₂O
At.wt. of water = (2 × 1) + 16 = 18
1 mole, water = 18 gr.
36g. of water = \(\frac{36}{18}\) = 2 moles

9th Class Physical Science 5th Lesson What is inside the Atom? 4 Marks Important Questions and Answers

Question 1.
Fill the blanks in the table using the given information. (Isotopes are not included).

Answer:

Question 2.
Fill in the missing information in the table given below.

Answer:

Question 3.
Draw the figures showing arrangement of electrons for the given elements.
1. Helium, Oxygen, Argon.
Answer:
1) Helium
2) Oxygen
3) Argon

2. How many neutrons are present in the nucleus of Sodium?
Answer:
Sodium = ²³₁₁Na
Neutrons = 23-11 = 12

Question 4.
a) Draw neat diagrams indicating the nucleus and arragement of electrons in different shell for the following elements?
i) Helium
ii) Carbon
iii) Argon
Answer:

b) Which of the above element is unstable? Why?
Answer:
Carbon is unstable. The nudes of carbon-14 atoms are unstable because they have too many neutrons relative to protons, so they gradually decay.

9th Class Physical Science 5th Lesson What is inside the Atom? Important Questions and Answers

9th Class Physical Science 5th Lesson What is inside the Atom? 1 Mark Important Questions and Answers

Question 1.
Write the names of isotopes of Hydrogen.
Answer:
Hydrogen, deuterium, tritium.

Question 2.
Which element has maximum number of isotopes?
Answer:
Cesium and Helium are the elements having maximum number of isotopes.

Question 3.
What is maximum number of electrons present in M-shell?
Answer:
Maximum number of electrons present in M-shell is 2 × 32 = 2 × 9 = 18.

Question 4.
Which atom doesn’t contain neutron in its nuclear?
Answer:
Hydrogen.

Question 5.
Show the arrangement of electrons in phosphorus through a diagram.
Answer:
Atomic number of phosphorus is 15.
Distribution of electrons : 2, 8, 5.

Question 6.
Who proposed rules for electron distribution in an atom?
Answer:
Bohr and Bury.

Question 7.
What is the first rule of Bohr and Bury for electron distribution in an atom?
Answer:
The maximum number of electrons present in a shell is given by the formula 2n², where ‘n’ is the shell number, which takes values 1, 2, 3, 4,

Question 8.
Write the second principle of Bohr – Bury.
Answer:
Each energy level or electron shell is further divided into sub-shells. The maximum number of electrons that can be accommodated in each shell is 8.

Question 9.
Write the third law of Bohr – Bury.
Answer:
Electrons cannot be filled in a given shell unless the inner shells are completely filled i.e., shells are filled in step-wise manner.

Question 10.
What is an octet?
Answer:
An outermost shell which has 8 electrons is said to possess an octet.

Question 11.
Define atomic number.
Answer:
Atomic number :
Atomic number is the number of protons in the nucleus of an atom, denoted by ‘Z’.

Question 12.
Define atomic mass number.
Answer:
Atomic mass number:
Atomic mass number is the number of protons plus the number of neutrons, denoted by A.
∵ A = Z + N

Question 13.
On the basis of Thomson’s model of an atom, explain how the atom is neutral as a whole.
Answer:
The negative and positive charges are equal in magnitude are present in atom. So, the atom as a whole is electrically neutral as whole according to Thomson model.

Question 14.
On the basis of Rutherford model of an atom, which sub-atomic particle is present in the nuclear of an atom?
Answer:
α – particles are repelled by the nucleus. So it contains positive charged particle that is proton.

9th Class Physical Science 5th Lesson What is inside the Atom? 2 Marks Important Questions and Answers

Question 1.
What are the postulates of Thomson’s model of the atom?
Answer:
J.J. Thomson proposed a model of atom in 1898. The main postulates are

1. An atom is considered to be a sphere of uniform positive charge and electrons are embedded into it.
2. The total mass of the atom is considered to be uniformly distributed throughout the atom.
3. The negative and the positive charges are supposed to cancel out the atom as a whole is electrically neutral.

This model is commonly known as plum pudding model or watermelon model.

Question 2.
What are the features of Rutherford’s model of atom?
Answer:
In 1909, Rutherford proposed a model of atom based on the alpha particle scattering experiment. The main features are

1. All the positively charged material in an atom formed a small dense centre, called the nucleus of the atom. The electrons were not a part of nucleus.
2. The negatively charged electrons revolve around the nucleus in well-defined orbits.
3. The size of the nucleus is very small as compared to the size of the atom.

This model is known as planetary model because the electrons revolve around the nucleus as planets revolve around the sun.

This model failed to explain the stability of atom.

Question 3.
Write the rules proposed by Bohr – Bury for electron distribution.
Answer:
Bohr-Bury proposed the following rules for electron distribution.
Rule – 1 :
The maximum number of electrons that can be accommodated in each shell is given by a formula 2n2. Where n is the shell number, which takes the values 1, 2, 3,….
Ex : For K shell, n = 1

∴ Maximum number of electrons in K shell = 2(1)2 = 2 × 1=2

Rule – 2 : Each energy level or electron shell is further divided into subshell. The maximum number of electrons that can be accommodated in each subshell is 8.

Rule – 3: Electron cannot be filled in a given shell unless the inner shells are completely filled.

Question 4.
Explain the distribution of electrons in oxygen atom using Bohr-Bury principle.
Answer:

1. Atomic number of oxygen is 8.
2. Hence it has 8 protons and 8 electrons.

Step -1 :
The K-shell can accommodate maximum 2 electrons, so the first 2 electrons fill the shell of n = 1.

Step – 2 :
The other 6 electrons will fill the higher shell n = 2 or the L-shell.
Step – 3 :
Then the electronic structure for oxygen atom is 2, 6.

Question 5.
Fluorine atom contains 7 electrons in the outermost shell. But its valency is ‘1’. Explain.
Answer:

• Valency is the number of electrons present in the outer most orbit of an atom.
• The distribution of electrons in fluorine (atomic number 9) is 2, 7.
• Hence the valency of fluorine could be 7.
• But it is easier to fluorine to gain one electron for becoming octet.
• Hence its valency is determined by subtracting seven electrons from 8 and which gives you a valency ‘1’ for fluorine.

Question 6.
What is the importance of valency?
Answer:
1) An atom with 8 electrons or an octet in their outer most shell is chemically stable or does not combine other atoms.
Ex : Ne, Ar, etc.

2) An atom with duplet or 2 electrons in its outer most shell is also more stable when there is only one shell present in it.
Ex : He

3) Atoms of an element thus react with other atoms. So as to achieve an octet in their shell.

4) When elements reacts to form compounds, their atoms must be combining in such a way that they can attain the stable electron distribution of noble gases or inert gases.

Question 7.
How can an atom achieve octet?
Answer:
An atom can achieve an octet by two ways.

1. One by transfer of electrons.
2. Other by sharing of electrons.
3. Both the processes results in the formation of bonds between atoms.

Question 8.
Explain the notation : \({ }_{9}^{19} \mathrm{F}\)
Answer:

• F is the symbol of element (Fluorine).
• 9 is the atomic number.
• 19 is the mass number.
• Hence fluorine has 9 protons and (19 – 9 = 10) 10 neutrons in its nucleus.
• 9 electrons are revolving around the nucleus.

Question 9.
Define isotope and give two examples.
Answer:
Isotope :
The atoms of the same element which have the same number of protons but have different number of neutrons are called isotopes.

Question 10.
“Sulphur shows multiple valency.” Explain this.
Answer:
a) Atomic number of sulphur is 16.
b) The distribution of electrons is 2, 8, 6.
c) Hence the valency should be ’6′.
d) But it is easier to sulphur to gain 2 electrons than loosing 6 electrons to become octet. Hence its valency would become 2.
e) So, sulphur shows multiple valency, i.e., ‘2’ or ‘6’.

Question 11.
Show the arrangement of electrons in first 18 elements schematically.
Answer:

Question 12.
What are the applications of isotopes in our daily life?
Answer:
Applications of isotopes :

1. Some isotopes are used for solving chemical and medical mysteries.
2. Isotopes are also commonly used in the laboratory to investigate the steps of a chemical reaction.
3. The isotope of uranium is used as a fuel in nuclear reactors.
4. The isotope of iodine is used in the treatment of goitre.
5. The isotope of cobalt is used in the treatment of cancer.

Question 13.
If an atom contains one electron and one proton, will it carry any charge or not?
Answer:
It will not carry any charge because proton is positively charged particle and electron is negatively charged particle. So they would neutralise each other.

Question 14.
What do you think would be the observation if the a – particle scattering experiment is carried out using a foil of metal other than gold?
Answer:
Gold has highest malleability and ductility. Extremely very thin foil can be prepared by using Gold, which is not possible with other metals. So, we will not get same type of results using other metals.

Question 15.
Helium atom has an atomic mass of 4u and two protons in its nucleus. How many neutrons does it have?
Answer:
Atomic mass due to protons = 2 × 1 = 2 u
Neutrons have almost same mass as protons.
Mass of neutrons = 4 – 2 = 2u
∴ Number of neutrons = 2

Question 16.
Write the distribution of electrons in carbon and sodium atoms.
Answer:
Distribution of electrons in carbon is 2, 4.
Distribution of electrons in sodium is 2, 8, 1.

Question 17.
If K and L shells of an atom are full, then what would be the total number of electrons in the atom?
Answer:
Number of electrons present in K shell = 2(1)² = 2 × 1=2
Number of electrons present in L shell = 2(2)² = 2 × 4 = 8
Total number of electrons in the atom = 2 + 8 = 10

Question 18.
If number of electrons in an atom is 8 and number of protons is also 8, then
i) what is the atomic number of atom?
ii) what is the charge on the atom?
Answer:
i) The atomic number of atom is 8.
ii) The electronic configuration of atom is 2, 6. By gaining two electrons it will get nearest inert gas configuration Neon. So, the charge on the atom is – 2.

Question 19.
Chlorine occurs in two isotopic forms that is \({ }_{17}^{35} \mathrm{Cl}\) and \({ }_{17}^{37} \mathrm{Cl}\). The percentage of these forms are 75% and 25% respectively. Find atomic weight of chlorine atom?
Answer:
The atomic mass of an element is taken as an average mass of all the naturally occurring atoms of the sample element.
The average atomic mass of chlorine atom on the bases of above data

Question 20.
For the symbol H, D and T tabulate three sub atomic particles found in each of them.
Answer:

Question 21.
Na⁺ has completely filled K and L shells. Explain.
Electron configuration of Na+ is 2, 8.
So, sodium has completed filled K and L shells because the maximum number of electrons filled in K and L shells are 2 and 8 electrons respectively.

Question 22.
If Bromine atom is available in the form of say, two isotopes \({ }_{35}^{79} \mathrm{Br}\)(49.7%) and \({ }_{35}^{81} \mathrm{Br}\) (50.3%), calculate the average atomic mass of Bromine atom.
Answer:

Question 23.
The average atomic mass of sample of an element X is 16.2 u. What are the percentages of isotopes \({ }_{8}^{16} \mathrm{X}\) and \({ }_{8}^{18} \mathrm{X}\)?
Answer:

∴ The percentage of first isotope is 90 and percentage of second isotope is 10.

Question 24.
If Z = 3, what would be the valency of the elements? Also, name the element?
Answer:
Electronic configuration of element is 2, 1 and the element is Lithium.
The element will get nearest inert gas Helium configuration by loosing one electron. So its valency is 1.

Question 25.
Composition of nuclei of two atomic species X and Y are given as under.

Give the mass number of X and Y. What is the relation between the two species?
Answer:
Mass number of X = 6 + 6 = 12
Mass number of Y = 6 + 8 = 14
So these two species have same atomic number (same number of protons) and different mass numbers. Therefore these two species are isotopes.

9th Class Physical Science 5th Lesson What is inside the Atom? 4 Marks Important Questions and Answers

Question 1.
How did the idea of sub-atomic particles evolve?
Answer:

• According to Dalton, atom is indivisible.
• But Michael Faraday’s experiments on electrolysis proved that atoms were acquiring negative charge during electrolysis.
• This is contradiction to Dalton’s theory.
• This lead to an idea that there must exist some tiny particles in atom which are responsible for atom to behave sometimes as charged particles.
• As atom is considered as electrically neutral, it probably had equal number of positive and negative constituents to maintain electrical neutrality.
• This gave scope to think about sub-atomic particles.

Question 2.
How do we determine the atomic mass of an element with its isotopes?
Answer:

• In nature, most elements occur as a mixture of two or more isotopes, each isotope has a certain percentage of natural occurrence.
• The atomic mass of an element is taken as an average mass of all the naturally occuring atoms of the sample element.
  Ex : Let us calculate the atomic mass of chlorine.
• Isotope of Cl occurs in nature, in two isotopic forms, with masses 35 units and 37 units.
• The isotope with mass 35 is present in 75% in nature.
• The isotope with mass 37 is present in 25% in nature.
• The average mass of chlorine is
  

Question 3.
Describe the Rutherford’s alpha particle scattering experiment. What are the conclu¬sions of this experiment.
Answer:

Rutherford conducted alpha particle scattering experiment in 1909 to study the atom.

1. The stream of alpha particles from a source having considerable energy is directed towards a very thin gold foil.
2. The gold foil was placed inside a detector in such a way that the detector would show a flash of light when an alpha particle struck it.
3. The entire arrangement was kept in a vacuum chamber.
4. Rutherford did not expect to see large deflections of alpha particles based on Thomson’s model.
5. But Rutherford observed the deflection of alpha particles through very large angles and a few alpha particles were reflected right back.
6. From this observation, Rutherford concluded as follows.

Conclusions :

1. Most of the space inside the atom is empty.
2. All the positive charge must be concentrated in a very small space within the atom and he named it as ‘nucleus’.

Question 4.
What information do you know from \({ }_{17}^{35} \mathrm{X}\)?
Answer:
Given that \({ }_{17}^{35} \mathrm{X}\)
a) The atomic number of element is 17.
b) Hence the element is chlorine, symbol is ‘Cl’.
c) Number of protons = 17.
d) Number of electrons = 17.
e) Mass number = 35.
f) Number of neutrons = 35-17 = 18
g) Distribution of electrons in shells

h) Valency is ‘l’.
i) It gains one electron to become octet.

SCERT AP Board 9th Class Social Solutions 16th Lesson Social Protest Movements Textbook Questions and Answers.

AP State Syllabus 9th Class Social Studies Solutions 16th Social Protest Movements

9th Class Social Studies 16th Lesson Social Protest Movements Textbook Questions and Answers

Improve Your Learning

Question 1.
Which of the following statements about lives of industrial workers are correct? And correct the false statements.
a) Workers controlled the industries.
b) Living conditions of the workers were comfortable.
c) Low wages was ones of the reasons for discontent among the workers.
d) During the phase of industrialization there was emphasis on emotions and feelings.
e) Romantic writers and artists tried to highlight values of closeness to nature as described in the folk tales and folk songs.
Answer:
a) False
b) False
c) True
d) False
e) True
Correction of false statements :
a) Workers did not control the industries.
b) Living conditions of the workers were not comfortable.
d) Duringthe phase of industrialization there was no emphasis on emotions and feelings.

Question 2.
List some of the problems faced by workers of those times. Discuss if such problems exist in our times too.
Answer:

• The workers were under the control of unsympathetic foreman and managers.
• There was no security for their lives and they lost their jobs. Working hours were long and unbroken.
• Wages were meagre and frequently owners tried to cut down wages or retrench workers or increase work load on them.
• The lifespan of the workers decreased.
• Workers were prone to accidents and no compensations were given.
• Workers used to live in slums and deaths were caused by spread of diseases.
• Children were taken as child labour in risky coal mines.

Present condition of workers :

• Salaries or wages are regularized.
• Factory regulation act prohibited children in coal mines. Later child labour is now prohibited.
• Working conditions are improved.
• Compensations are paid for accidents or deaths but it is very less.

Question 3.
Write a paragraph comparing the ideas of capitalism and socialism. How were they similar or different?
(OR)
Distinguish between socialism and capitalism.
(OR)
Compare and contrast between Socialism and Capitalism.
(OR)
What are the differences between captalism and socialism?
Answer:

Question 4.
How was the idea of equality being similar or differently challenged by women and workers movements?
Answer:

1. Workers demands regarding equality –
   a) Equality of opportunities, status, etc., irrespective of birth status.
   b) Opposed discrimination of any sort.
2. The idea of equality challenged by women –
   a) Equality of opportunities to all public dignities, offices and employments.
   b) They demanded equal access to property.
   c) They demanded equal access to civil rights such as voting …. etc.

Question 5.
Draw a poster to illustrate the ideas of “liberty, equality and justice” with in the context of workers and women. Identify occasions where these idea are being violated.
Answer:

In the following occasions the ideas are violated.

• Still the wages given to women labour are low when compared with men.
• Even domestic violence against women is still not able to be controlled.
• Assaults against women are seen everywhere.
• Certain job opportunities are available only for men.

Question 6.
Locate the countries in the world map in which the protest movements took place.
Answer:
The protest movements took place in the following countries.

1. USA
2. England
3. France
4. Germany
5. Italy
6. India
7. China
8. Russia

Question 7.
Read the last paragraph of page 203 and first paragraph of page 204 and comment on them.

Answer:

• The status of women in India has been subject to many great changes over the past few millenia.
• From equal status with men in ancient times though the low points of the medieval period, to the promotion of equal rights by many reformers, the history of women in India has been eventful.
• In modern India women have held high offices including that of the President, Prime Minister, Speaker, etc.

Question 8.
Do you find any social protest movements around you? Interview with the leaders of that movement and prepare a report and present in your class.
Answer:
Yes I found a social movement in my surrounding Area. That is “Prohibition”.
Students : Good morning Madam
Leader (Lady) : Good morning Children
Students : Madam, why did you start the movement on prohibition?
Leader : Because to protect the human beings.
Students : How did you protect them?
Leader : If we start a movement against the liquor, then the government will stop the production.
Students : Why did the government to stop the production of liquor.
Leader : Liquor it is the harmness to the health of the consumer. And how much the worker earn half ofthe amount they spend on liquor. Not spend for his family.
Students : Is it known to the government or not.
Leader : Yes, it is known by government. But they did not take any steps. That’s why we started movement for the safe of families.
Students : How far this movement is helpful to families?
Leader : Children, 90% of our families in India are poor. They are not able to fulfill they proper basic needs also. But they addict to liquor and spoil their life and health and they did not take care about families and education of their children. Gradually, the families become a poor, due to the movement they stop the use of liquor, and use the money for the welfare ofthe family and live happily.
Students : Very good Madam, how did you raise the movement?
Leader : I create awarness among the family members who affected these and gathered and maintain a group and started the movement.
Students : Did you successful any?
Leader : Yes, due to the movement government ban on “cheap liquor”. That’s why we continue our movements to “complete prohibition.”
Students : Very good Madam, you are doing a great job for society. So, we also participated in this movement.

9th Class Social Studies 16th Lesson Social Protest Movements InText Questions and Answers

Question 1.
In what ways do you think ideas of liberty, equality and fraternity wouid have helped to inspire protest movements? (Text Book Page No. 198)

• Industrialization deeply affected the working class.
• Human values were lost.
• There was less scope for dignity and security of life.
• Workers started protesting against their conditions.
• The spread of new political ideas of “liberty”, “equality” and “fraternity” pioneered by the French Revolution gave boost to the protest movements.
• The workers inspired by these ideas demanded
  a) “Liberty” from the bonds of capitalists.
  b) “Equality” of opportunities irrespective of social status.
  c) “Fraternity” inspired them to fight for their dignity.

Question 2.
The government passed a law which provided capital punishment to those who broke machines. Do you think this was justified? (Text Book Page No. 199)
Answer:
No. Giving capital punishment for these who broke machines was not justifiable.

Question 3.
In what way did Marx’s Socialism disagree with Luddism? (Text Book Page No. 202)
Answer:

• Luddism is social protest movement.
• It demanded minimum wages, control over the labour of women and children.
• Demanded work for those who lost jobs because of coming of machines.
• It also demanded right to form trade unions.

Socialism as profounded by Karl Marx

• He wanted production to be an all-society affair rather than a matter of one family.
• He gave importance to collective interest.
• He forced workers not only to fight for better wages but for ending the capital system itself.
• He argued that workers should organize themselves and throughout the capitalists.

Question 4.
Why did Marx consider factory production as superior and desirable? (Text Book Page No. 202)
Answer:

• Marx believed that industrial production is progressive because it has made possible the industrial transformation of the world.
• Marx believed that industrial production made it possible for people to live and earn their livelihood.
• Factory production enabled us to work on small scale too.

Question 5.
What was the main difference between Marx and the earlier socialists? (Text Book Page No. 202)
Answer:
Marx asserts that revolution, which is a political action, is the only way to achieve socialism.

But according to early socialist, reforms and peaceful means are the best way to achieve socialism.

That was the main difference.

Question 6.
Do you think people have achieved ideas of “liberty, equality and fraternity” in the 21st century? (Text Book Page No. 198)
Answer:

• Modern states are welfare states.
• They always provide their people with the ideas of liberty.
• These ideas are included in the constitution itself.
• Now the people have
  a) Liberty of thought and expression.
  b) Equality irrespective of caste, sex, religion and race.
  c) “Fraternity” which protects their dignity.

Question 7.
In India too such laws which protected our farmers from competition from import of cheap agricultural products are being ended. Do you think such imports will benefit the poor people in India? (Text Book Page No. 198)
Answer:
No. I do not think so. Such imports will not benefit poor people in Inaienjecauseney may cause damage to our production also.

Question 8.
Why do you think workers would have supported the ending of the ComLawsandwhy do you think the landowners supported them? (Text Book Page No. 198)
Answer:
The artificially high corn prices encouraged by the Corn Laws meant tnatuiewomng class had to spend the bulk of their income on corn just to survive. Since they had no income. Left over for other purchases, they could not afford manufactured goods. Thus the economical spiral worsened for everyone involved. So the workers would have supported the ending of the Corn Laws.

The beneficiaries of the Corn Laws were the nobility and the other large land holders. Landowners had vested interest in seeing the Corn Laws remain in force. The voting members of parliament had no interest in repeating the Corn Laws. So the landowners supported them.

Question 9.
To what extent do you think breaking the machines helped the workers? (Text Book Page No. 199)
Answer:

• The breakingof machines did not give any direct and immediate benefit to the workers.
• Rather they were given punishments like death sentence or life imprisonment.
• Of course it had long term benefit like their right against exploitation, right to express their views and right to job security were recognized.

Question 10.
Do you see any social movements which are still inspired by these idea round you? (Text Book Page No. 198)
Answer:
A) Yes, so many social movements are inspired by the ideas of “liberty, equality and fraternity”. Some of them are-

1. Social movement of protection of tribals rights is based on the principles of equality.
2. “SC”s demands of equality of opportunity is one of the social movements.
3. “Assault” against “women” in Delhi has led to a mass social movement. That has resulted in the enactment of ‘Nirbhay Act”.
4. “Prohibition of children in factories or any other work” is also based on these ideas.

Question 11.
When new machines are brought in a factory, some workers are usually rendered jobless. Why do you think this happens ? Can there be ways of improving technology without creating unemployment for workers? (Text Book Page No. 199)
Answer:

• A machine can perform the work of 100 workers in lesser time.
• Hence when new machines are brought in a factory, some workers usually rendered jobless.
• When new technology is introduced new jobs are created.
• Therefore, workers should be given propertrainingin “technical know how” to get new job opportunities.

SCERT AP Board 9th Class Social Solutions 22nd Lesson Women Protection Acts Textbook Questions and Answers.

AP State Syllabus 9th Class Social Studies Solutions 22nd Women Protection Acts

9th Class Social Studies 22nd Lesson Women Protection Acts Textbook Questions and Answers

Improve Your Learning

Question 1.
What are the disadvantages of child marriage?
Answer:
Disadvantages of child marriage :

• Underage pregnancy.
• Provision for trafficking and sale of girls.
• Pushing the unmatured into family system.
• Increased abortions, premature births which results not only infant mortality but also the death of mothers.
• Handicapped child births or dead child births.
• Mental as well as physical health problems.
• Obstacle to education.
• Hurdle for physical growth (especially regarding female).
• Become child labourers for family maintenance.

Question 2.
Why has domestic violence become a common practice? In what forms domestic violence is seen? Find out the reasons.
Answer:
Reasons for the domestic violence which became common practice :

1. The family system in the society is on the edge of a blade.
2. No moral values are taught to the children.
3. Lack of understanding capacity in the people.
4. Changing cultures in the society.
5. Hurting manner.
6. Lack of adjustment between family members.
7. Lack of respect towards women.
8. Uncontrolled anger, i.e. mental imbalance.

Question 3.
You have read about various problems girls and women. Have you noticed any sort of problems in your village/town? Specify them and what is to be done.
Answer:
I observe the following in our area.

1. An estimated 85 to 90 percent of domestic violence victims are females.
2. Females are victims of intimate partner violence at a rate about five times that of males.
3. Females between the ages of 16 and 24 are most vulnerable to domestic violence.

To control this domestic violence –

1. Proper counselling should be given to them.
2. Value oriented education should be taught to the children.
3. The nature of thinking from others’ point of view’ should be developed from childhood.

Question 4.
Many acts are made by the government. What do you suggest for better implementation?
Answer:
The Acts cause changes physically. But there should be a change in the minds of the people. The government should take necessary steps for this change.

Question 5.
Write an essay on general problems, the women facing.
Answer:
A Thomson Reuters Foundation expert poll last year ranked India as the world’s fourth most dangerous country for a woman, behind only Afganisthan, Congo, and Pakisthan.

Even though the practice is outlawed 300,000 to 600,000 female foetuses are aborted every year in India because of the preference for boys.

From the time they are born or not born and continuing till late in life when they become wives or mothers, it’s a vicious cycle of discrimination and violence keeps on continuing.

Nearly half of Indian girls are married off before the age of 18. Girls are also seen as a financial liability. The practice of dowry is banned by the government, but it’s still as common as ever.

A 2012 of UNICEF study found more than half of Indian males think it is justifiable to beat a wife under certain circumstances.

Outside the household, crimes against women in India are also on the rise, and the evidence is shocking. According to government data, more than 24,000 cases of rape were reported in 2011.

Indian women in some ways, have also made some strides. Literacy rates have gone up, maternal mortality rates have gone down, and millions of women have joined the workforce.

Authorities acknowledge that action is needed and say they are taking steps to try to better protect women.

Helplines have been set up. A number of fast track courts have also been established because of the December 16 gang rape, exclusively for cases of sexual assault and rape. But women’s rights activists say that when discrimination begins even before birth, change will not come easily.

Question 6.
Imagine that you are Tehsildar. How would you prevent child marriages?
Answer:
As a Tehsildar –

1. I will raise the awareness in parents and their relatives.
2. If they don’t listen to me, I will request the police department to take them into custody. Thus I will prevent child marriages.

Question 7.
Prepare a pamphlet to understand the problems faced by the women.
Answer:

Women in India

Women in Independent India are comparitively in a respectable position. Some of the problems which had been haunting the community of women for centuries are not found now.
But still, for a woman, her life is a battle for survival and dignity from her birth to death. Female infanticide, eve-teasing, sexual exploitation, sexual harassment, rapes are still common. There are still many areas where women have not equal rights and are not encouraged to take up education. Dowry practice is still rampant, eventhough it termed illegal. Women still have to make a lot of sacrifices in every areas of their lives.

Question 8.
Read the paragraph under the title ‘Sexual Assault and Torturing’ of page 275 and comment on it.

Sexual Asssault an Torturing :
Recently, central government has appointed Justice J.S. Verma Committee asking suggestions to prevent sexual assault and abuse. Based on the suggestions, Hon. President of India issued an ordinance on 2nd February, 2013. Some important features of the ordinance, are;

• Minimum 20 years of imprisonment.
• Recruitment of women police to address the complaints from the victims.
• It is not necessary for the victim to attend before the police officers individually.
• There will be no punishment if the accused dies in struggle at the time of attack with acid on women.
• There is scope to short video at the time of complaining and trial on the request of the victims.

Answer:

1. Only legislation and law enforcement agencies cannot prevent the incident of crime against women.
2. There is a need of social awakening and change in the attitude of masses, so that due respect and equal status is given to women.

Question 9.
What facilities does the government provide to the poor for seeking judicial justice?
Consult a lawyer and get the information.
Answer:

• Lok Adalat is a relatively recent product in the justice for the poor.
• Next to that there are Legal Aid Committees, Legal Services Authority.

Services offered by the legal services authority :

1. Payment of court and other process fee,
2. Changes for preparing, drafting and filing of any legal proceedings.
3. Changes of a legal practitioner or legal advisor.
4. Costs of obtaining decrees, judgements, orders or any other documents in a legal proceeding.
5. Costs of paper work, including printing, translation, etc.

These are the facilities provided by the government to the poor for seeking judicial justice.

9th Class Social Studies 22nd Lesson Women Protection Acts InText Questions and Answers

Question 1.
Have you ever seen child marriages? (Text Book Page No. 269)
Answer:
No, I have never seen child marriages.

Question 2.
Have you ever observed harassment and violence made to women and girls? (Text Book Page No. 269)
Answer:
Yes, I have observed in many of my neighbouring houses.

Question 3.
Have you ever observed the various types of domestic violence threatening women in day to day life? (Text Book Page No. 269)
Answer:
I have observed the following,

1. Persisting denial of food,
2. Insisting on perverse sexual conduct
3. Constantly locking a woman out of the house.
4. Denying the woman access to children, thereby causing mental torture.
5. Physical violence.
6. Taunting, demoralising and putting down the woman with the intention of causing mental torture.
7. Abusing children in their mother’s presence with the intention of causing her mental torture.
8. Mental abuse (threaten to harm, stopping from jobs, force to marry whom she doesn’t like).
9. Threatening divorce unless dowry is given.

Question 4.
What shall we do to stop such violence caused to girls and women? (Text Book Page No. 269)
Answer:
We should take the following steps to stop such violence to girls and women.

1. Value oriented education should be given to the children in schools.
2. The persons, who caused violence, should be punished.

Question 5.
Have you ever seen or heard about women being tortured for dowry in your locality? How are they being tortured? What sort of suggestions do you make to prevent? Who will held responsible? (Text Book Page No. 273)
Answer:
Yes, I have seen such a case. My neighbour ‘Vasu’ is harassing his wife for dowry. He has his mothers support also. They usually beat her, abuse her. I suggest her to proceed women protection cell authorities. Then the project officer will hold responsible.

Question 6.
Domestic violence takes place now and then and gradually it becomes a bad habit pattern. More violence generates from violence. How do we stop this? Who will help? (Text Book Page No. 274)
Answer:
In order to put a stop to the domestic violence, there are various things which should be followed.
1) Awareness:
To make the people aware about the drawbacks and harms of the domestic violence, setthe rules againstthe practice and impose stringent punishments to the attacker.

2) Need for stringent laws:
It is very important that the law against domestic violence has to be imposed stringently.

3) Empowered non-government organizations:
Individuals can also seek the help of NGOs.

4) Seek police help:
In case of severe violence, individuals can seek legal help from the police and put an end to domestic violence.

5) Be aware of the domestic violence facts:
The facts of the domestic violence should be learnt by all.

6) Encourage and not threaten:
It is very important to organize a meeting and encourage people to come up with the solutions.

7) Counselling :
It is very important to have counselling in terms of danger.

Question 7.
Sometimes child marriages are performed for the under aged i.e., less than 15 years without their consent. How do we stop such marriages? Who will help us? (Text Book Page No. 271)
Answer:
We can approach the higher officials in the area – to stop the child marriages.

1. District Collector at district level.
2. R.D.O at division level
3. Tehsildar or Mandal level ICDS officer.
4. Gram Panchayat Secretary at village level are the incharges in stopping the child marriages. They will help us.

SCERT AP Board 9th Class Social Solutions 3rd Lesson Hydrosphere Textbook Questions and Answers.

AP State Syllabus 9th Class Social Studies Solutions 3rd Lesson Hydrosphere

9th Class Social Studies 3rd Lesson Hydrosphere Textbook Questions and Answers

Improve Your Learning

Question 1.
Find the odd one out and give an explanation for your choice.
i) a) evaporation
b) condensation
c) salination
d) precipitation
Answer:
Odd one – (c)
Except salination, remaining all belong to the water cycle.

ii) a) tectonics
b) centrifugal force
c) solar energy
d) precipitation
Answer:
a) Tectonics is odd one : Remaining all are the factors that cause ocean currents.

Question 2.
Correct the false statements.
a) Oceans trenches can be located near the continents.
b) Relief features of the oceans are like plains.
c) Most salt in the seas is washed into it from the land over centuries.
d) Temperature of ocean water remains the same across the globe.
Answer:
a) Ocean trenches are the deepest parts of the ocean floor.
b) Relief features of the oceans are Trenches, Deep sea plains and Ridges.
c) True.
d) Temperature of ocean water varies from place to place across the globe.

Question 3.
Describe any one impact of ocean currents for the region you live.
Answer:
The Indian Monsoon current refers to the seasonally varying ocean current regime found in the tropical regions of the northern Indian ocean. The seasonally reversing open ocean currents that pass through south of India are referred to as the winter monsoon current and the summer monsoon current, alternately the north-east monsoon current and the southwest monsoon current.

India receives rainfall due to these currents.

Question 4.
Do you think that the description of blue planet is accurate? Describe any one way in which your activity impacts its oceans.
Answer:
Yes, I do think that the description of blue planet is accurate.

Humans are a part of the natural environment. But our activities lead to degradation of environment.

Oceans are suffering from our activities too, our land practices cause agricultural runoff, sewage, and litter to end up in the oceans daily. Today oceans have also fallen victim to our exploitation. Many large fishes like whales have been disappearing. Damage to oceans is damage to our livelihoods, well-being and nourishment.

Question 5.
Why differences are there in the salinity of oceans?
Answer:

• Salinity of ocean water depends upon many causes, but the main cause is continuous movement of ocean. Water from one place to other due to rotation of earth and winds which takes water here and there causing change in salinity of ocean water (ocean currents and thermohaline currents)
• Melting of ice causes an influx of fresh water, which dilutes ocean water.
• inflow of river water causes an influx of fresh water, which dilutes ocean water.
• Evaporation is only fresh water, which removes fresh water flow an area, causing salt to become more concentrated.
• Rain and snowfall opposite of evaporation, we are adding fresh water and diluting it.
• Wave and wind – various local mixing causes smaller – scale variation in surface salinity.

Question 6.
How is human life dependent upon oceans?
(OR)
How is human life depends on Oceans?
(OR)
How are oceans influencing human life?
Answer:

• Oceans stabilize climates over land.
• They are the storehouses of many chemicals, each of which are useful to humans.
• They disperse many plant & animal species from one continent to another, making biota available in various places. Many of these plants & animals are used as food, neutraceutically as medicines.
• Some people constantly live on boat, due to paucity of land in such areas.
• They are a source of various types of poly-metallic nodules.
• They are used for landing of certain debris of satellites & safely pad most of the meteors that come from outer space, as oceans cover more than 75% of earth’s surface.

Question 7.
Observe the map 1 on page 35 and write down the names of a few warm and cold currents.
Answer:
Some warm and cold currents :

1. Equatorial current (warm)
2. Gulf stream (warm)
3. Labrador current (cool)
4. Greenland current (cool)
5. North Pacific current (warm)
6. West wind drift (cool)
7. East wind drift (cool)
8. Bengula current (warm/cool)

Question 8.
Read the para ‘Ocean as a Resource’ on page 33 and comment on it.
Ocean as a ResourceMost life on earth is under the water. Human beings still have not finished identifying all the different forms of life in the oceans. Human beings have depended on oceans for their food and livelihood from the ancient times. Oceans provided abundant food resources like fish and salt. We also use the sand, gravel, etc. for our industries or housing. Humans extract minerals like chlorine, fluroine, iodine from it. Ocean waves are used for generating power. Ocean floor is mined for oils. Oceans also provide us with gems and pearls. For centuries, we have created our civilisations on its shores and traded across with each other travelling on them.
Answer:
The ocean is one of earth’s most valuable natural resources. It provides food in the form of fish and shell fish. It is used for transportation – both travelling and shipping. It provides a treasured source of recreation for humans. It is mined for minerals and drilled for crude oil.

Question 9.
Prepare a flow chart which shows different land forms.
Answer:

Question 10.
Prepare a list of currents which are found in the Pacific, Atlantic and Indian oceans. Identify the cold and warm currents in different oceans.
Answer:

9th Class Social Studies 3rd Lesson Hydrosphere InText Questions and Answers

Question 1.
Give the reasons for the Sow salinity of Baltic sea. (Text Book Page No. 32)
Answer:

1. Baltic sea is a brackish mediterranean sea located between Central and Northern Europe.
2. The Baltic sea’s salinity is much lower than that of ocean water.
3. Baltic is a small sea on a global scale.
4. The causes for the low salinity of the Baltic sea are
   a) The abundant fresh water run off from the surrounding land.
   b) The shallowness of the sea.
   c) The flow of fresh water into the sea from approximately two hundred rivers and the introduction of salt from the south builds up a gradient of salinity in the Baltic sea.
   d) The Baltic sea is only connected to the world’s oceans by the narrow and shallow waters of the Sound and Belt-sea.
   e) This limits the exchange of water with the North sea and means that the same water remains in the Baltic for a lot of years.

For all the above reasons the salinity of the Baltic sea is less than that of the salinity of the oceans.

SCERT AP Board 9th Class Social Solutions 21st Lesson Human Rights and Fundamental Rights Textbook Questions and Answers.

AP State Syllabus 9th Class Social Studies Solutions 21st Human Rights and Fundamental Rights

9th Class Social Studies 21st Lesson Human Rights and Fundamental Rights Textbook Questions and Answers

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Question 1.
Which of the following is not an instance of an exercise of a fundamental right
a) Workers from Bihar go to Punjab to work on the farms
b) Religious minority set up a chain of schools
c) Men and women government employees get the same salary
d) Parents’ property is inherited by their children
Answer:
d) Parents’ property is inherited by their children

Question 2.
Which of the following freedoms is not available to an Indian citizen?
a) Freedom to criticise the government
b) Freedom to participate in armed revolution
c) Freedom to start a movement to change the government
d) Freedom to oppose the central values of the Constitution
Answer:
b) Freedom to participate in armed revolution

Question 3.
Which of these statements about the relationship between democracy and rights is more valid? Give reasons for your preference.
a) Every country that is a democracy gives rights to its citizens.
b) Every country that gives rights to its citizens is a democracy.
c) Giving rights is good, but it is not necessary for a democracy.
Answer:
I prefer the first sentence. The reasons are –
a)

1. All democratic countries ensure certain rights to its citizens.
2. Rights are reasonable claims of the people.
3. Democratic governments strive to preserve equal ground for all.

b)

1. During the early days of modern history, all despotic governments granted certain rights to the people. That was done under great pressure.
2. Therefore every country that gives rights to its citizens is not a democratic.

c) The rights are so important that they are also expressed by many democratic countries and codified by the UNO and find first place in the universal declaration of human rights. Hence it is necessary for democracy to give rights.

Question 4.
Are these restrictions on the right to freedom justified? Give reasons for your answer.
a) Indian citizens need permission to visit some border areas of the country for reasons of security.
b) Outsiders are not allowed to buy property in some areas to protect the interest of the local population.
c) The government bans the publication of a book that can go against the ruling party in the next elections.
Answer:
a)

1. Yes, it is justifiable.
2. It is the responsibility of the government to protect the life of the people.
3. Border areas are high risk areas and tension always persists there.
4. Hence permission is necessary.

b)

1. No, not justifiable.
2. People in democracy have freedom to reside in any part of India.
3. Hence, this statement is against the fundamental rules.
4. But, there is one clause in our Constitution itself, that we cannot buy property in the state of Jammu and Kashmir.
5. So Jammu and Kashmir is an exemption to the fundamental rule.

c)

1. No, not justifiable.
2. Democracies grant civil liberties to its citizens.
3. Under civil liberties, we can express our ideas through media or books.
4. But generally, government bans certain books in order to avoid internal tensions.

Question 5.
Look through this chapter and the previous one and make a list of the six Fundamental Rights in the Constitution.
(OR)
What are fundamental rights? How are these helping us to live better?
(R)
Write any four fundamental rights enjoyed by the citizens of India.
Answer:
There are six fundamental rights. They are :

1. Right to equality
2. Right to freedom
3. Right to religious freedom
4. Right against exploitation
5. Right to education and culture
6. Right to constitutional remedies.

Fundamental rights protect the liberties and freedom of the citizens against any invasion by the state, prevent the establishment of the authoritarian and dictatorial rule in the country. They are very essential for the all-round development of the individuals and the country.

Question 6.
Are the Fundamental Rights being violated in each of the following cases? If so, which Fundamental Right or Rights? Discuss with your classmates.
a) Suppose a person is kept in a police station for 4 days without being told the reasons, which law was broken?
b) Suppose your neighbor tries to claim some of your land as her own.
c) Suppose your parents do not allow you to go to school. They make you take up a job in a match factory instead because they cannot afford to feed you properly.
d) Suppose your brother refuses to give you the land that you have inherited from your father.
Answer:
a)

1. In the first case, arresting a person without proper reason and keeping in a police station for 4 days is against the fundamental rights.
2. “Rights to life” and personal liberty ensures that “no one can be arrested without being told the grounds for his arrest.
3. “Hebeaus Corpus” writ protects the individuals from the arrest.

b)

1. Occupation of one’s land by another is not a violation of fundamental rights.
2. Right to property is a legal right.

c)

1. Not allowing a child to go to school is definitely violation of fundamental right.
2. “Right to education” is a part of “right to life”.
3. Government is responsible for providing free and compulsory education to all the children up to the age of 6 to 14 years.

d)

1. Refusal on part of your brother to give you land that you inherited is not violation of fundamental rights.
2. Right to property is a legal right and civil courts will solve the problem.

Question 7.
Suppose you are an advocate. How would you argue the case for a group of people who come to you with the following request:
“The river in our area is getting very polluted by the factories upstream. We get our drinking water from the river. People in our villages keep falling ill because of the polluted water. We have complained to the government but there has been no action from their side. This is surely a violation of our Fundamental Rights.” ;
Answer:

• Being an advocate I would like to file a writ in the court for the interests of the public.
• This is surely a violation of our fundamental rights.
• Hence I argue the case in such a way that immediately stay order would be issued to close down the factory.
• When the government did not respond to our complaints, courts would definitely safeguard our interests.

Question 8.
Read the paragraph under the heading ‘Abolition of Title’ and answer the following question:
Abolition of Title:
In another move to remove arbitrary and unequal classification of the aristocratic class and the bourgeoise, the Constitution prohibits the State from conferring any titles. The British government had created an aristocratic class known as Rao Bahadurs and Khan Bahadurs in India -these titles were also abolished. Citizens of India cannot accept titles from a foreign State. However, military and academic distinctions can be conferred on the citizens of India. The awards like the Bharat Ratna, the Paramveer Chakra, and the Padma Vibhushan cannot be used by the recipient as a title and do not, accordingly, come within the constitutional prohibition.
The awards can’t be used by the recipient as a title. Why?
Answer:

• In order to remove arbitrary and unequal classification of the aristocracy and middle class, the constitution prohibits the state from conferring any titles.
• Hence the awards like the Bharat Ratna, the Padma Vibhushan cannot be used by the recipients as a title.

Question 9.
Analyse an incident you know about where the Fundamental Rights are violated.
Answer:

• The 1984 Anti-Sikh Riots was a four-day period during which sikhs were massacred by members of the secular-centrist Congress party of India, some estimates that more than 2000 were killed. (Religious violation)
• Dalits and indigeneous peoples continue to face discrimination, exclusion and acts of communal violence.
• Narco analysis test (against to the Indian constitution), “nobody may be made a witness against himself, etc.

Question 10.
Invite a senior advocate into your classroom and collect the following information by conducting an interview.
– violation of fundamental rights and its consequences
– violation of children rights
– ways of struggle for rights in democracy
– any other related
Answer:
Students : Good morning sir.
Advocate : Good morning children.
Students : Sir, today we are going to known about the fundamental rights and importance of other rights from you sir.
Advocate : Yes, children, I will explain. What do you know about.
Students : Sir what will happen, if we violate fundamental rights.
Advocate : Courts will punish us.
Students : Sir please explain one example?
Advocate : If any person is created a nusence in the public places, he created inconvience to the freedom of other people. Then the police arrested that person and kept in the prision.
Students : What will happen when violate the children’s rights?
Advocate : Children are the tomorrow’s citizens generally 6-14 years age is considred as children. So that age children should be in school. But if they did not go to school and work in any where the owner will punish by government / court. Parents should provide education to their children. That is their fundamental right.
Students : Sir what are the ways to struggle for rights in democracy?
Advocate : Students in a democracy always we are fighting for our rights. We will achieve our rights in a peaceful manner. So movements will be in a democratic manner not in a violent manner. These are in through petitions, strikes etc.
Students : Sir please explain any other related issues.
Advocate : Children fundamental rights are provided by our constitution. We will enjoy that not violate and not create any inconvienient to others it will we create any we will punish by government and lost our valuable future also.
Students : Thank you sir.
Advocate : Ok children. Bye.

9th Class Social Studies 21st Lesson Human Rights and Fundamental Rights InText Questions and Answers

Question 1.
Write a few important features of Preamble you studied last year. (Text Book Page No. 256)
Answer:
The Preamble is the heart and soul of our constitution. The important features are –

1. The Preamble starts with the words “We the people of India”. This ensures that sovereignty vests with the people.
2. It also confirms or ensures justice, equality, liberty, and fraternity to all its citizens.
3. It declares our country as sovereign, socialistic, secular, democratic, republic. Each of the words have different meaning.

Question 2.
What kinds of rights to equality does the Constitution ensure? Give examples. (Text Book Page No. 259)
Answer:
The Constitution ensures the following rights to equality to its citizens.

1. Equal protection of law * The laws apply to all in the same manner, regardless of a person’s income, status, background, etc.
2. Social Equality – The state condemns any sort of discriminations of human beings.
3. Equality of opportunity – The constitution guarantees equality of opportunity for all citizens regarding education or employment.
4. Abolition of untouchability.
5. Abolition of titles – In order to remove inequalities “Titles” of any sort are abolished.

Question 3.
What would happen if the Fundamental Right to Equality was not in the Constitution? Discuss. (Text Book Page No. 259)
Answer:

1. Democratic systems preserve equal grounds for all.
2. Democracies work on the principle of equality which is also known as “rule of law”.
3. If the fundamental “Right to equality” was not in the Constitution, the very essence of democracy would be lost.

Question 4.
What associations are there in your area? (Text Book Page No. 261)
Answer:
There are so many associations in my area. Some of them are –

1. Teachers Associations
2. Workers Association
3. Foremen’s Association
4. Students’ Associations
5. Auto – Rickshaw Association
6. Trade Union Associations
7. Rice Millers’ Associations
8. Fishermen’s Associations, etc.

Question 5.
Why are workers’ unions formed? What problems do they face? (Text Book Page No. 261)
Answer:
Workers unions are formed to protect the rights of workers and to solve their problems. These unions hold meetings to discuss their problems and take their demands to the officers of the factory. The following are their problems.
a) Their working conditions will not be healthy.
b) Salaries, dearness allowances, pensions, etc., will not be paid to them in time.
c) Sometimes their services will not be regularised.
d) They will not provide any educational facilities to their children of the factory workers.
e) Medical reimbursement, generally, not given to them.

Question 6.
Why do people want to move and settle in various parts of the country? (Text Book Page No. 261)
Answer:
In search of job opportunities people move and settle in various parts of the country.

Question 7.
What do you remember about the difference between the role of the police and that of the court? (Text Book Page No. 262)
Answer:

• Police generally file a case on any person who had committed a crime.
• He has to submit the accused in the case before the court.
• The court decides whether a person is guilty or not. And finally gives judgement.

Question 8.
What are the different types of schools you see in your area? Why do you think are there such different types of schools? (Text Book Page No. 262)
Answer:
There are the following types of schools
Basing on the management –

1. Zilla Parishad School
2. Mandal Parishad Schools
3. Government Schools
4. Social Welfare Schools
5. Tribal Welfare Schools
6. Government aided schools
7. Private Schools

Basing on the classes –

1. Primary Schools (I class to 5th class)
2. Upper Primary Schools (1st class to 7th class)
3. High Schools (6th class to 10th class)

The children, whose parents are rich and can afford private school, go to private schools. And rest of the children generally go to government schools.

Question 9.
Can anyone not follow any religion if he/she wishes? (Text Book Page No. 263)
Answer:
No, everyone can follow whatever religion they want. “Right to religious freedom” is our fundamental right.

Question 10.
State some instances of violations of Human Rights. (Text Book Page No. 266)
Answer:

1. Arbitrary arrests
2. Denial of right to information and corruption
3. Sexual cruelty
4. Rape of women
5. Delay in investigation of crimes
6. Female infanticide
7. Kidnapping for ransom
8. Deplorable conditions of women, children and downtrodden people
9. Discrimination against women in the family
10. Cruelty to domestic servants

The above are some instances of the violations of human rights. These violations continue unchecked because people are not aware of their human rights.

Question 11.
Read the passage and answer the following questions. (Text Book Page No. 262)
The Constitution states, “no child below the age of 14 shall be employed to work in any factory or mines or engaged in any other hazardous employment.” Accordingly, laws have been made that prohibit children from making matches, crackers, beedis, and carpets, or doing printing and dyeing, etc.
Do you think this right has been made available to children in the villages and cities in your area?
Answer:
There are number of children who are still working in small scale industries like dyeing, printing, beedi making etc.

Question 12.
Discuss whether you think each of the following is a violation of the Fundamental Right to Equality, Also discuss whether you think it is constitutionally right or wrong to do such things. (Text Book Page No. 259)

• While filling water from a public source, some people object if the vessel of another person touches their pots.
• Some communities are never provided a place to live within the village but always outside.
• In some schools, certain children are not allowed to serve water because they belong to a particular caste.
• Members of some communities do not go to many places of worship because they fear that they will be ill treated or beaten up.

Answer:

• The above examples are the clear evidences of practice of untouchability.
• The practice of untouchability is a crime.
• Anyone doing so is punishable under law.

Question 13.
With the help ofthe teacher find out the minimum wages in your state. (Text Book Page No. 262)
Answer:
Minimum wages were received by the people in different sector in our state.
Male – Rs. 200 (per day) – Female – Rs. 150 (per day)
Teacher – Rs. 300 to 2000 (per day).

Agriculture labour
Male – Rs. 180 (per day)
Female – Rs. 120 (per day)

Mason
Male – Rs. 300 (per day)
Female – Rs. 180 (per day)

Question 14.
How does the practice of “Sati” violate fundamental rights? (Text Book Page No. 263)
Answer:

• No citizen can be denied his life and liberty except by law.
• “The right to life” does not include “the right to die”, and hence suicide, forced death or sati, etc. are offences.
• “Sati”, hence, is violation of fundamental right of “the right to live”.

Question 15.
What is the responsibility of the government towards workers who are able to find some work, in the city but don’t have a proper place to live? (Text Book Page No. 261)
Answer:

• Our Government has introduced subsidised housing schemes to the people of below poverty line.
• Under urban basic schemes, Indira Aavas Yojana, Rajiv Gruha Yojana, etc., so many people acquired houses.
• They are constructed in the prime localities of the cities.
• Most of the slums in the cities were removed.
• Development is still going on in this regard.

Question 16.
Write a petition to the NHRC if you know any instances of human rights violation in your area. (Text Book Page No. 266)
Answer:

Question 17.
Is there a State Human Rights Commission in our state? Find out about its activities. (Text Book Page No. 266)
Answer:
Yes, there is a State Human Rights Commission in our state.
A Human Rights Commission, also known as a Human Relations Commission is a body set up to investigate, promote or protect human rights.

Its activities are

1. Inquire into any violation of human rights.
2. Look into negligence in the prevention of human rights violation by a public servant.
3. They can take cognizance either sumotu or on a petition presented to it or on an order of a court.
4. They intervene in any proceeding involving allegation of violation of human rights pending before a court etc.

AP State Syllabus AP Board 9th Class Physical Science Important Questions Chapter 1 Motion.

AP State Syllabus 9th Class Physical Science Important Questions 1st Lesson Motion

9th Class Physical Science 1st Lesson Motion 1 Mark Important Questions and Answers

Question 1.

From the above data, what can you say about the motion of the object?
Answer:
The object is in the uniform motion and its speed is constant.

Question 2.
Frame any one question to understand Newton’s third law of motion.
Answer:
How does rocket engine work?

9th Class Physical Science 1st Lesson Motion 2 Marks Important Questions and Answers

Question 1.
Distinguish between speed and velocity. jawjMB
Answer:

Question 2.
What happens to the speed and the direction of motion of a ball rolling down an inclined plane?
Answer:

1. Speed of the rolling ball changes.
2. But the direction of motion remains constant.

Question 3.
A motor cyclist drive from A to B with uniform speed of 30 km/hour and returns back with a speed of 20 km/hour. Find the average speed.
Answer:
Speed of the motor cyclist from A to B = 30 km/hr.
Speed of the motor cyclist from B to A = 20 km/hr.

Question 4.
A train of length 100 m. is moving with a constant speed of 10 m/s. Calculate the- time taken by the train to cross the electric pole.
Answer:
Length of the train = 100 m; Speed of the train = 10 m/s
Time taken to cross the elctrical pole (t) = s/v = \(\frac{100}{10}\) =10 sec.
[∵ Distance travelled while crossing an electrical pole = Length of the train]

Question 5.
Calculate the average speed of “Ussahi Bolt” who sprints 100m in 9.81 sec. during 2016 Rio Olympics to win Gold medal.
Answer:
Distance covered by Ussain Bolt = 100 m
time = 9.81s.

Question 6.
Explain the terms in the formula v = u + at.
Answer:
v = u + at
u = initial velocity
v = final velocity
a = acceleration
t = time

9th Class Physical Science 1st Lesson Motion Important Questions and Answers

9th Class Physical Science 1st Lesson Motion 1 Mark Important Questions and Answers

Question 1.
Define uniform acceleration.
Answer:
Acceleration is uniform when in equal intervals of time, equal changes in velocity occur.

Question 2.
Write an equation of motion to find the distance travelled when initial velocity, time, and acceleration are given.
Answer:
s = ut + \(\frac{1}{2}\) at²

Question 3.
Draw a displacement vector from Visakhapatnam to Hyderabad to the following diagram.

Answer:

Question 4.
Difine acceleration.
Answer:
The rate of change of velocity in an object is known as its acceleration.

Question 5.
What is the key difference between distance and displacement?
Answer:
Distance is the length of the path traversed by an object in a given time interval and displacement is the shortest distance covered by the object in a specific direction.

Question 6.
The distance travelled by a particle in time’t’ is given by s = (2.5 m/s²) t². Find the average speed of the particle during the time ‘O’ to ‘5’ sec.
Answer:
The distance travelled by the particle from 0 to 5 sec is s = 2.5 m/s² × 5² = 62.5 m

Question 7.
A table clock has its minutes hand 4 cm long. Find the average velocity of the tip of the minute hand between 6.00 AM to 6.30 AM.
Answer:
The minute hand of a clock comes into a straight line from 6.00 AM to 6.30 AM.
Hence the displacement of the minute hand S = 2 x 4 = 8 cm
Time = 30 minutes = 1800 sec.

Question 8.
A ball is thrown up with an initial speed of 4m/sec. Find the maximum height reached by the body.
Answer:

Question 9.
The adjacent distance – time graph indicates
A) A particle travels constantly along X-axis.
B) Particle is at rest.
C) The velocity of the particle increases up to a time t0 and then remains constant.
D) The particle travels up to time t(( with constant velocity and then stops.

Answer:
C

Question 10.
A man used his car. The initial and final odometer readings are 4849 and 5549 respectively. The journey time is 70h. What is average speed of the journey?
Answer:
Distance covered = 5549 – 4849 = 700 km. ; Time = 70 h.

9th Class Physical Science 1st Lesson Motion 2 Marks Important Questions and Answers

Question 1.
An object is moving in a circular path of radius 7 m. What is the distance and displacement of an object after one revolution ?
Answer:
Radius (r) = 7 m
22
Distance covered by object = 2πr = 2 × \(\frac{22}{7}\) × 7 = 44 m
The object come back to original position displacement of the object is 0.

Question 2.
An object reaches other end of a diameter in a circular path of radius 7 m in 7s. Find speed and velocity of the object?
Answer:

Question 3.
A person moves 3 km towards east and turned toward north and travelled a distance of 4 km. Find total distance and total displacement.
Answer:

Question 4.
An object completes 1/4th revolution of a circular path of radius r. Then find the ratio of distance and displacement.
Answer:

Question 5.
a) What is a vector? Give example.
b) What is a scalar? Give example.
Answer:
a) Vector :
The physical quantity which is specified with magnitude and direction is called a vector.
Eg : Displacement, velocity are vectors.

b) Scalar :
The physical quantity which does not require any direction for its specification is called ‘scalar’.
Eg : Distance, time are scalars.

Question 6.
How does a vector represents? Explain.
Answer:

1. A vector can be represented as a directed line segment.
2. It’s length indicates magnitude and arrow indicates it’s direction.
3. Vector is represented by an arrow as shown in the figure.
   
   Here point ‘A’ is called tail and point ‘B’ is called head.

Question 7.
Bhavan did not recognise the difference between 40 meters displacement and distance. Then Anitha ex- plained the difference by asking some questions to Bhavan. What would be those questions?

Note : She used this diagram.
Answer:
By using the diagram Anitha asked the following questions :

1. What is the distance between A and D?
2. Which is the shortest distance from A to D?
3. What is the direction of an object if it travelled in the route A → B → C → D? Can you determine its direction?
4. On which direction the distance is short from A to D? Measure it.
5. Which path has specified direction?
   Either A → B → C → D or A → D?
6. Which path has specified magnitude?
   Either A → B → C → DorA → Dor Both?
7. Which is the shortest, distance among the two paths?
8. If the displacement has both magnitude and specified direction, which path is considered as a displacement?
9. What is the difference between distance and displacement?

Question 8.
What happens to the direction of velocity and acceleration when the
i) speed of an object increases?
ii) speed of an object decreases?
Answer:
i) If the speed of an object increases, the direction of velocity and acceleration are one and the same.
ii) If the speed of an object decreases, the direction of velocity and acceleration are in opposite directions. Here, at a certain instant the speed becomes zero.

Question 9.
Draw a displacement vector and a velocity vector to the given path of motion of a body.

Answer:

Question 10.
Find the acceleration of a bus if its speed increases from 0 m/s to – 600 m/s in 1 minute?
Answer:

The acceleration of the bus is 10 m/sec².

9th Class Physical Science 1st Lesson Motion 4 Marks Important Questions and Answers

Question 1.
Distinguish between distance and displacement.
Answer:

Question 2.
Explain the terms uniform and non-uniform motions.
Answer:
Uniform motion :

1. If a body covers equal distances in equal intervals of time, assuming the direction of motion is constant, then the motion is said to be uniform motion.
2. The motion of a body is said to be uniform when its velocity is constant.
3. The s -1 graph for a uniform motion is a straight line.
4. Ex : Motion of hands in a clock.

Non-uniform motion :

1. If a body covers unequal distances in equal intervals of time, assuming the direction of motion is constant, then the motion is said to be non-uniform motion.
2. A body is said to be in non-uniform motion if its velocity changes with time.
3. The s -1 graph for non-uniform motion is not a straight line.
4. Ex : Motion of a car/bus between two stations on a road.

Question 3.
Derive equations of uniform accelerated motion.
Answer:
1) Let ‘u’ be the velocity at the time t = 0 and V be the velocity at the time’t’ and let ‘s’ be the displacement covered by the body during time’t’ as shown in figure.
2) From the definition of uniform acceleration,

Question 4.
Describe the graphical method to calculate the instantaneous speed at a given point.
Answer:

1. Consider a car moving along a straight road with varying speed.
2. Take time elapsed on X – axis and distance cov¬ered on Y – axis and plot a graph for its motion at regular intervals of time.
3. A general case of motion with varying speed is shown in the figure.
4. The average speed during the time interval from
   
5. Then we calculate average speed for a very short time interval encompassing the time at an instant t3 which is so short interval, that value of average speed would not change materially if it was made even shorter.
6. The instantaneous speed is represented by the slope of the curve at a given instant of time.
7. The slope can be found by drawing a tangent to the curve at that point.
8. The slope of the curve gives speed of the car at that instant.

Question 5.
What is difference between speed and velocity?
Answer:

Question 6.
Derive s = ut + \(\frac{1}{2}\) at²
Derive one equation for displacement of a body which is in the uniform acceleration.
Answer:
1) Let u be the initial velocity,
v be the velocity at time ‘t’.
a be the acceleration,
s be the displacement

Question 7.
A car travelled from A to E station in 3 minutes. Viewing path given below in the figure. find
i) distance
ii) displacement
iii) speed
iv) velocity

Answer:
i) Distance = AB + BC + CD + DE = 540 + 460 + 540 + 260 = 1800 m

ii) Displacement = Distance between A and E

Question 8.
Give an example to each situation in daily life.
i) Speed changes when direction remains constant.
ii) Direction of motion changes when speed remains constant.
iii) Speed and direction simultaneously change.
Answer:
i) The palk taken by a ball which was released from the top of the inclined plane. Here the direction of motion remains constant but velocity gradually increases.

ii) Whirl a stone which is tied to the end of the string continuously.
Here it’s direction of motion changes but speed remains constant.

iii) The path taken by a stone, which was thrown into the air.
Here speed and direction of the motion both changes simultaneously.

AP State Syllabus AP Board 9th Class Physical Science Solutions Chapter 11 Sound Textbook Questions and Answers.

AP State Syllabus 9th Class Physical Science Solutions 11th Lesson Sound

9th Class Physical Science 11th Lesson Sound Textbook Questions and Answers

Improve Your Learning

Pick out the correct answer :

Question 1.
When we say sound travels in a medium (AS 1)
A) the medium travels
B) the particles of the medium travel
C) the source travels
D) the disturbance travels
Answer:
D) the disturbance travels

Question 2.
A sound wave consists of (AS 1)
A) number of compression pulses only
B) number of rarefaction pulses only
C) number of compression and rarefaction pulses one after the other
D) vacuum only
Answer:
C) number of compression and rarefaction pulses one after the other

Question 3.
Hertz stands for oscillations per (AS 1)
A) second
B) minute
C) hour
D) milli second
Answer:
A)second

Question 4.
When we increase the loudness of sound of a TV, the property of sound that changes is (AS 1)
A) amplitude
B) frequency
C) wavelength
D) speed
Answer:
A) amplitude

Question 5.
The characteristic of the sound that describes how the brain interprets the frequency of sound is called (AS 1)
A) pitch
B) loudness
C) quality
D) sound
Answer:
A) pitch

Question 6.
In a stethoscope, sound of heart beats travel through stethoscope tube (AS 1)
A) by bending along the tube
B) in a straight line
C) undergoing multiple reflections
D) all of the above
Answer:
C) undergoing multiple reflections

Question 7.
Explain the following terms : (AS 1)
a) amplitude
b) wavelength
c) frequency
Answer:
a) Amplitude :
The maximum variation in density or pressure from the mean value is called amplitude.
(or)

The maximum disturbance of particles of a medium from their mean position is called amplitude.

b) Wavelength :
The distance between two consecutive compressions or two consecutive rarefactions is called the wavelength of a sound wave, denoted by W. Wavelength is measured in ‘meters’.

c) Frequency :

1. The number of oscillations of the density of the medium at a place per unit time is called the frequency of the sound wave.
2. Frequency is denoted by ‘o’.
3. The S.I. unit of frequency is ‘Hertz’.

Question 8.
Deduce the relation between wavelength, frequency, and speed of sound. (AS 1)
Answer:
1) Speed of sound can be defined as the distance by which a point on the wave, such as a compression or rarefaction, travels in unit time.

2) Let the distance travelled by a wave in T seconds = X metres

3) The distance travelled by a wave in 1 second = \(\frac{\lambda}{\mathrm{T}}\) meters

4) Thus by definition of speed of wave, v = \(\frac{\lambda}{\mathrm{T}}\) ……….. (1)

5) We know that frequency and time period are related as υ = \(\frac{1}{T}\) ……….. (2)

6) From (1) and (2) we get v = λ .υ
∴ Speed of sound = Frequency × Wavelength

Question 9.
How are multiple reflections of sound helpful to doctors and engipeeps? (AS 7)
Answer:
1) Doctors use multiple reflections of sound to hear the sounds produced with in the body using stethoscope.

2) Doctors can see the images of patient’s organs like liver, gall bladder, uterus, etc. to know the abnormalities in their functioning, using ultrasounds.

3) Engineers use the reflections of sound in designing concert halls and cinema halls.

4) Generally the ceilings of concert halls, conference halls, cinema halls are designed such that sound after reflection reaches all corners of the hall as shown in the figure.

Question 10.
Name two quantities that vary periodically at a place in air as a sound wave travels through it. (AS 1)
Answer:
The two quantities that vary periodically at a place in air as a sound wave travels through it are density and pressure of particles.

Question 11.
Which has larger frequency – infrasonic sound or ultrasonic sound? (AS 7, AS 2)
Answer:

• Infrasonics are the sounds of frequency less than 20 Hz.
• Ultrasonics are the sounds of frequency greater than 20 kHz.
• Hence the ultrasonics have larger frequency.

Question 12.
The grandparents and parents of two-year-old girl are playing with her in a room. A sound source produces a 28 kHz sound. Who in the room is most likely to hear the sound? (AS 2, AS 7)
Answer:

• The two-year-old girl is able to hear the sound.
• Children can hear sounds of somewhat higher frequencies up to 30 kHz.

Question 13.
Does the sound follow same laws of reflection as light does? (AS 1)
Answer:

• Reflection of sound follows the same laws as the reflection of light when sound is reflected.
• The directions in which the sound is incident and reflected make equal angles with the normal to the reflecting surface.

Question 14.
Why is soft furnishing avoided in concert halls? (AS 7)
Answer:

• Sound reflects like the reflection of light.
• But unlike to light, sound reflects more on rough surfaces than soft surfaces.
• In concert halls, sound must undergo multiple reflections, so as to reach all corners of the hall.
• Hence for better reflection, soft furnishing is avoided in concert halls.

Question 15.
Two sources A and B vibrate with the same amplitude. They produce sounds of frequencies 1 kHz and 30 kHz respectively. Which of the two waves will have larger power? (AS 1)
Answer:
Frequency of source A = 1 kHz; Frequency of source B = 30 kHz

As the speed of wave increases with frequency and both the waves have same amplitude, the sound produced from source B has larger power.

Question 16.
What do you understand by a sound wave? (AS 1)
Answer:

• Sound is produced from a vibrating body.
• It travels through air in the form of a wave.
• Sound waves are longitudinal.

Question 17.
Define the wavelength of a sound wave. How is it related to the frequency and the wave speed? (AS 1)
Answer:
Wavelength :
The distance between two consecutive compressions or rarefactions is called wavelength.

Relation between wavelength, frequency, and wave speed :

1. Speed of sound can be defined as the distance by which a point on the wave, such as a compression or rarefaction, travels in unit time.
2. Let the distance travelled by a wave in T seconds = λ metres
3. The distance travelled by a wave in 1 second = \(\frac{\lambda}{\mathrm{T}}\) meters
4. Thus by definition of speed of wave, v = \(\frac{\lambda}{\mathrm{T}}\) ………… (1)
5. We know that frequency and time period are related as o = \(\frac{1}{T}\) ……….. (2)

Question 18.
Explain how echoes are used by bats to judge the distance of an obstacle in front of them. (AS 1)
Answer:

• Bats search out prey and fly in dark night by emitting and detecting reflections of ultrasonic waves.
• The high pitched ultrasonic squeaks of the bat are reflected from the obstacles or prey and returned to bat’s ear.
• The nature of reflections tells the bat where the obstacle or prey is and what it is like.
• The bats use ultrasound for navigation and location of the food in dark.

Question 19.
With the help of a diagram describe how compression and rarefaction pulses are produced in air near a source of sound. (AS 5)
Answer:

• Consider a vibrating membrane of a musical instrument like a drum or tabla.
• As it moves back and forth, it produces a sound.
• The figure shows the membrane at different instants and the condition of the air near it at those instants.
• As the membrane moves forward, it pushes the particles of air in the layer in front of it.

• So, the particle of air in the layer get closer to each other, hence the density increases.
• This layer of air pushes and compresses the layer next to it and so on.
• We call this disturbance as compression pulse.
• When the membrane moves backward, it drags back the layer of air near it. Hence the density decreases.
• The particles of air in the next layer on the right move into fill this less dense area.
• This is a rarefaction pulse moves to right.
• As the membrane moves back and forth repeatedly, compression and rarefaction pulses are produced, one after the other.
• These two pulses travel one behind the other, carrying the disturbance with it.

Question 20.
How do echoes in a normal room affect the quality of the sounds that we hear? (AS 7)
Answer:

• Echo is a reflected sound, arriving at the position of listener more than 0.1s after the direct sound.
• Quality is the characteristic of a sound which enables us to distinguish between musical notes emitted by different musical instruments.
• In a normal room, if echo is formed, we can hear multiple sounds, at same time.
• Our ear cannot perceive and judge the sound from where it is coming.
• So, quality of sound does not work here.

Question 21.
Explain the working and applications of SONAR. (AS 1)
Answer:

• SONAR stands for Sonographic Navigation And Ranging.
• This is a method for detecting and finding the distance of objects under water by means of reflected ultrasonic waves.

Working of SONAR:

1. SONAR system consists of a transmitter and a detector in the “Observation Centre” on board of a ship.
2. From the observation centre, ultrasonic waves of high frequency are sent in all directions under the water through transmitter.
3. These waves travel in straight lines till they hit an object such as a submarine, a sunken ship, etc.
4. The waves are then reflected and are received back by the receiver at the observation centre.
5. The study of these reflected waves gives information about the direction of the object located.
6. The time between sending ultrasonic wave and receiving its echo, the distance of the object is calculated.
7. Reflections from various angles can be utilized to determine the shape and size of the object.

Mathematical expression :

1. Let’d’ be the distance between SONAR and an underwater object.
2. ‘t’ be the time between sending an ultrasonic wave and receiving its echo.
3. ‘u’ be the speed of sound in water.
4. The total distance covered by the wave from the SONAR to the object and back is 2d.
5. From the equation s = ut ⇒ 2d = ut ⇒ d = \(\frac{ut}{2}\).

Application:
Marine geologists use this method to determine the depth of the sea and to locate underwater hills and valleys.

Question 22.
Find the time period of a source of a sound wave whose frequency is 400 Hz. (AS 1)
Answer:
Frequency υ = 400 Hz
Time period T =?

Question 23.
A sound wave travels at a speed of 340 m/s. If its wavelength is 2 cm, what is the frequency of the wave? Will it be in the audible range? (AS 1)
Answer:
Speed of sound v = 340 m/s.; Wavelength λ = 2 cm = 0.02 m.
Frequency υ =?

The audible range of sound wave is 20 Hz to 20 kHz.
Hence this is in the audible range.

Question 24.
Given that sound travels in air at 340 m/s, find the wavelength of the waves in air produced by a 20 kHz sound source. If the same source is put in a water tank, what would be the wavelength of the sound waves in water? (AS 7)
Speed of sound in water = 1,480 m/s.
Answer:
In air:
Speed of sound wave (v) = 340 m/s ; Frequency of source of sound (o) = 20 kHz
Wavelength of the sound wave λ =?
v = υλ

∴ Wavelength of the sound wave in air = 17 m

Same source is kept in water :
∴ Speed of sound in water (v) = 1480 m/s
Frequency of sound wave (p) = 20 kHz
Wavelength of sound wave λ =?
v = υλ

∴ Wavelength of the sound wave in water = 74 m

Question 25.
A man is lying on the floor of a large, empty hemispherical hall, in such a way that his head is at the centre of the hall. He shouts “Hello!” and hears the echo of his voice after 0.2 s. What is the radius of the hall ? (Speed of sound in air 340 m/s) (AS 7)
Answer:
Let the distance travelled by the sound wave = 2d m

As the head of the man is at the centre of hemispherical room, then ‘d’ is the radius of the hall.
∴ Radius of the hall = 34 m

Question 26.
“We know that sound is a form of energy. So, the large amount of energy produced due the sound pollution in cosmopolitan cities can be used to our day-to-day needs of energy. It also helps us to protect biodiversity in urban areas”. Do you agree with this statement? Explain.
Answer:

1. Sound is a form of mechanical energy.
2. So, the mechanical energy can be converted into electrical energy.
3. Experiments are going on this concept.
4. If this is successful, we have the following benefits.
   a) Sound pollution can be controlled.
   b) Conventional methods of producing electrical energy from coal or water will cause in loss of biodiversity. This can be avoided.
   c) Natural resources like water can be protected.
   d) Increasing needs of energy can be overcome by this method.

Question 27.
How do you appreciate efforts of a musician to produce melodious sound using a musical instrument by simultaneously controlling frequency and amplitude of the sounds produced by it.
Answer:

• The sounds which produce pleasing effect on the ear are called musical sounds.
• Any instrument which produces musical sound is called musical instrument.
• The person who plays a musical instrument to produce melodious sound is called a musician.
• The musician must have control on breathing, concentration on the output of the sound, which is a very hard task.
• For this the musician needs a lot of practise.
• With the musician’s practise and knowledge over musical notes only we can hear melodious sound otherwise it could only be a noise.
• Hence the efforts of a musician are highly appreciable.

Question 28.
You might have observed that sometimes your pet dog starts barking though no one is seen near in its surroundings or no disturbance heard nearby. Does this observation raise any doubts in your mind about the peculiar behaviour of dog after your understanding about ‘range of hearing the sound’. If yes, write them.
Answer:

• Dogs can hear sounds of frequencies up to about 50 kHz, which is ultrasonic.
• After hearing this ultrasonics, a dog will bark panicly, though no one is seen near.
• I understood this after studying about ‘range of hearing the sound’.
• Before the knowledge of ‘range of hearing the sound’, I felt that the dogs are barking by seeing some devils, which is a misconception.
• Scientific knowledge helps us to know reasons for many misconcepts.

Question 29.
Find out the names of animals (and their photographs from internet) which communicate using infra-sonic or ultra-sonic sound and prepare a scrap book.
Answer:
Scrap book

9th Class Physical Science 11th Lesson Sound InText Questions and Answers

9th Class Physical Science Textbook Page No. 184

Question 1.
How does sound reach our ears from the source of its production?
Answer:
Soufid travels in the form of waves. It reaches our ears from the source of its production, in the form of waves.

Question 2.
Does it travel by itself or is there any force bringing it to our ears?
Answer:
Sound does not travel by itself. When a sound is produced, the kinetic energy of the source, vibrates the nearest particles in the medium. These particles transfers energy and finally, it reaches our ears.

Question 3.
What is sound? Is it a force or an energy?
Answer:
Sound is a form of energy.

Question 4.
Why don’t we hear sounds when our ears are closed?
Answer:
When our ears are closed, the energy in the form of waves reaches our ear, but it cannot make the eardrum to vibrate. Hence we cannot hear the sound.

Question 5.
Why is the light ray dancing, after sound is made in the tin?
Answer:
The dancing of light ray, after the sound is made in the tin shows that the sound travels in the form of waves from the source of its production.

Question 6.
What do you infer from this?
Answer:
Sound is a form of energy which can travel in the form of waves through the medium.

Question 7.
Can we say that sound is a form of mechanical energy?
Answer:
Yes, sound is a form of mechanical energy.

9th Class Physical Science Textbook Page No. 185

Question 8.
Do you hear any sound?
Answer:
We cannot hear any sound.

Question 9.
Do you see any vibrations in the tuning fork?
Answer:
Yes, we can sense the vibrations in the tuning fork.

Question 10.
What do you conclude from the above activity?
Answer:
We observe that vibrating tuning fork produces sound.

Question 11.
Can you produce sound without vibration in the body?
Answer:
We cannot produce sound without vibration in the body.

Question 12.
Give some examples of vibrating bodies which produce sound.
Answer:
Drums, tabla, calling bell, school bell, etc.

Question 13.
What part of our body vibrates when we speak?
Answer:
When we speak, vocal cord vibrates in our body.

Question 14.
Do all vibrating bodies necessarily produce sound?
Answer:
All vibrating bodies produce sound, but we cannot hear some of them, due to the limit of audible frequency.

9th Class Physical Science Textbook Page No. 186

Question 15.
If sound travels in the form of a wave then what is the pattern?
Answer:
Sound travels in the form of longitudinal or transverse waves in the air or in the other material.

9th Class Physical Science Textbook Page No. 188

Question 16.
What do you say about sound waves in air by the above activity?
Answer:
From the above activity, we can say that there involves change in the density of medium while sound waves are travelling in air.

Question 17.
Are they longitudinal or transverse?
Answer:
Sound waves in air are longitudinal.

Question 18.
Does sound get reflected at the surface of a solid?
Answer:
Yes, sound gets reflected at the surface of a solid as in the case of reflection of light.

Question 19.
What happens if you lift your tube slightly above the table?
Answer:
If we lift the tube slightly we cannot hear the sound clearly.

Question 20.
Are able to listen to the sound? If not why?
Answer:
We are unable to hear the sound. If we lift one of the pipes then the pipe carrying incident sound, the pipe carrying reflected sound will not be in the same plane. Hence we cannot hear the sound.

9th Class Physical Science Textbook Page No. 195

Question 21.
Do hard surfaces reflect sound better than soft ones?
Answer:
Generally, hard surfaces reflect sound better than soft surfaces. But sound reflects quite well from rough surfaces than polished surfaces.

9th Class Physical Science Textbook Page No. 187

Question 22.
Do compressions and rarefactions in sound wave travel in same directions or in opposite directions? Explain.
Answer:

• Compressions and rarefactions in a sound wave will be in opposite direction.
• In a compression, all the particles come close, so the density and pressure increases.
• In a rarefaction, all particles drag back, so the density and pressure decreases.
• In a microscopic view of particle, the compression and rarefaction travel in opposite directions.

9th Class Physical Science Textbook Page No. 191

Question 23.
Does the frequency of sound waves depend on the medium in which it frawels? How?
Answer:
Yes.

2) As speed of wave differs from medium to fnedium, the frequency also changes, keeping the wavelengths constant.

Question 24.
The frequency of source of sound is 10 Hz. How many times does it vibrate in one minute?
Answer:
Number of vibrations per second = 10
Number of vibrations in one minute = 10 × 60 = 600

Question 25.
Gently strike a hanging bell (temple bell) and try to listen to the sound produced by it with a stethoscope keeping it both at bottom portion and top portion of the bell. Is the pitch and loudness of the sound same at the two portions? Why?
Answer:
No. The bob of the bell strikes at the bottom portion of the bell. Hence the pitch and loudness are high.

Question 26.
During a thunderstorm if you note a 3 second delay between the flash of lightning and sound of thunder. What is the approximate distance of thunderstorm from you ?
Answer:
Time taken to reach the sound = 3 s ; Speed of sound in air = 343.2 m/sec.
Distance of thunderstorm = 343.2 x 3 = 1029.6 m

9th Class Physical Science Textbook Page No. 194

Question 27.
Two girls are playing on identical stringed instruments. The strings of the both instruments are adjusted to give notes of same pitch. Will the quality of two notes be same? Justify your answer.
Answer:
If the two girls are playing with same instruments, then the quality is same. If the girls are playing with different stringed instruments the quality will be different.

Quality is the characteristic which enables us to distinguish between musical notes emitted by different musical instruments.

Question 28.
What change, would you expect in the characteristic of a musical sound when we increase its frequency one instance and amplitude in another instance?
Answer:
When frequency is increased, the pitch of sound increases. When amplitude is increased, its loudness increases.

9th Class Physical Science Textbook Page No. 195

Question 29.
What could be the reason for better reflection of sound by rough surfaces than polished surfaces?
Answer:

• Sound reflects better on rough surfaces than polished surfaces.
• The rough surface reflects sound in all directions, so it can reach in many directions.

9th Class Physical Science Textbook Page No. 196

Question 30.
Why is an echo weaker than the original sound?
Answer:

• Echo is the reflected sound.
• While it travels back, it gradually loses its energy.
• Hence the echo is weaker than original sound.

Question 31.
In a closed box if you say hello, the sound heard will be Hellooooo ………. What does it mean?
Answer:
In a closed box, the multiple reflections of sound has no way to go out side. Hence we will hear the sound as hellooooooo ………

9th Class Physical Science Textbook Page No. 197

Question 32.
What is the advantage of having conical openings in horns, megaphones, etc?
Answer:
The conical openings in horns, megaphones, etc. will guide the reflected sound waves in forward direction and spreads towards the audience.

Question 33.
Why do we put cushions on the chairs, carpet on the floor, straw materials on the walls in cinema halls?
Answer:

• These materials absorb unnecessary reflections of sound, so that we can hear more clearly.
• As these material absorb reflected sound waves, the people outside the cinema halls, cannot hear the sound produced in the cinema hall.

9th Class Physical Science Textbook Page No. 199

Question 34.
What is the benefit of using ultrasound over light waves in the above applications?
Answer:

• Light waves cannot penetrate in the internal organs like liver, kidney, etc.
• Light wave after reflection do not form image.
• Ultrasound waves can penetrate through internal organs like liver, kidney, etc.
• After reflection, ultrasound waves produce image. So, in ultrasonography and surgeries, ultrasound waves are better than light waves.

9th Class Physical Science 11th Lesson Sound Activities

Activity 1

Question 1.
How can .you say that the sound is a form of energy?
Answer:

1. Take a tin can and remove both ends to make a hollow cylinder.
2. Take a balloon and stretch it over the can.
3. Wrap a rubber band around the balloon.
4. Take a small mirror and stick it on the balloon.
5. Take a laser light and let it fall on the mirror.
6. After reflection the light spot is seen on the wall.
7. Now shout directly into the open end of the can and observe the dancing light.

Observations:

1. When sound is made, the energy produced from the sound vibrates the membrane of the balloon, resulting in the dancing of light ray.
2. This shows that sound is a form of energy which travels in air.

Activity – 2

Question 2.
Prove that the sound is produced from a vibrating source.
Answer:

1. Attach a small piece of steel wire to one of the prongs of a tuning fork as shown in the figure.
2. Strike the tuning fork with a rubber hammer.
3. While it is vibrating, try to draw a straight line on a piece of smoked glass as quick as possible with, it.
4. Keep the end of the wire in such a way just it touches the glass.
5. A line is formed in the form of a wave.
6. Repeat the experiment when the tuning fork is not vibrating and observe the difference in the line.

Observations:

1. We have produced vibrations in the tuning fork by striking it with a hammer.
2. Thus the vibrating tuning fork produces sound.
3. Thus the sound is produced by vibrating bodies.

Activity – 3

Question 3.
а) How do you demonstrate the formation of compressions and rarefactions in a slinky?
Answer:

1. Take a slinky.
2. It is a spring-shaped toy which can be extended or compressed very easily.
3. Lay it down on a table or the floor as shown in figure.
4. Ask a friend to hold one end.
5. Pull the other end to stretch the slinky and then move it to and fro along its length.
6. We will see alternate compressions and rarefactions of the coil.
7. This is similar to the pattern of varying density produced in a medium when sound passes through it.

b) Mow do you demonstrate the formation of crests and troughs in a slinky?
Answer:

1. Hang a slinky from a fixed support.
2. Hold it gently at the lower end and quickly move your hand sideways and back.
3. This will cause a hump on the slinky near the lower end.
4. The hump travels upwards on the slinky as shown in the figure.
5. The humps formed alternately are known as crests and troughs.

Activity – 4

Question 4.
Describe an activity to listen the reflected sound.
Answer:

1. Take two long, identical tubes and place them on
2. Ask your friend to speak softly into one tube while you use the other tube to listen.
3. Adjust the tube until you hear the best sound.
4. You will find that you hear your friend’s voice best when the tube makes equal angles with a normal to the wall.
5. This shows that reflection of sound follows the laws of reflection of light.
6. Lift your tube slightly above the table.
7. You will not be able to listen the voice clearly, because the plane carrying the incident wave and reflected wave are changed.
8. Repeat the experiment by placing flat objects of different materials (steel and plastic trays, a card board, a tray wrapped with cloth, etc.) against the wall and observe the changes in the sound.

Observations:

1. Reflection of sound follows the laws of reflection of light.
2. When the plane carrying incident wave and reflecting wave changes, the reflected sound cannot be heard clearly.
3. Hard or rough surfaces reflect the sound better than soft surfaces.