AP State Syllabus AP Board 8th Class Physical Science Important Questions Chapter 6 Sound

## AP State Syllabus 8th Class Physical Science Important Questions 6th Lesson Sound

### 8th Class Physical Science 6th Lesson Sound 1 Mark Important Questions and Answers

Question 1.
What is sound? How does sound produces?
Answer:
Sound is a form of energy. A vibrating body produces sound.

Question 2.
Honeybee produce peculiar sound through their mouth or some other organ used for that purpose?
Answer:
A honeybee can’t make a sound using vocal cords. The buzzing sound that you b*ear from any flying insect is caused by vibration of their wings when flying.

Question 3.
Length of vocal cords in men is nearly 20 mm, in women it is about 5 cir1 less. Whereas in children it is shorter. Can we say that the length of vocal cords plays any role in deciding the quality of sound produced by men, women and children?
Answer:
Yes, we can say that the length of vocal cords decreases then the shrillness °f sound increases.

Question 4.
Pitch of the voices of the following is in ascending order. Lion < adult man < adult woman < child < infant < insect. Can you guess the reason why?
Answer:
The pitch of the voices depend on frequency. As the number of vibrations per second increases the pitch or shrillness increases. So insect produce shrillness due to more frequency of vibration.

Question 5.
Do you find any difference in blowing the whistle and striking the drum?
Answer:
Whistle has more shrillness due to its higher frequency than drum which has less frequency.

Question 6.
Why are some sounds loud?
Answer:
The sounds which have greater amplitude are louder.

Question 7.
Why are some sounds feeble?
Answer:
The sounds which have low amplitude are feeble.

Question 8.
Is there any relation between the intensity of sound and vibrations of the body which produces sound?
Answer:
As amplitude of vibration increases the intensity of sound increases.

Question 9.
How many times is a car horn more powerful than near total silence?
Answer:
It is 1011 times more powerful than a near total silence.

Question 10.
How many times is a jet engine more powerful than a smallest audible sound?
Answer:
It is 1012 times more powerful than a smallest audible sound.

Question 11.
What is a vibration?
Answer:
The to and fro motion of a body from its mean position is known as vibration.

Question 12.
What is amplitude?
Answer:
The maximum displacement of vibrating body from its mean position is called amplitude.

Question 13.
What are the parts of the speech organ which involved in producing sounds?
Answer:

1. Vocal cords
2. Lips
3. Teeth and tongue
4. Nose and throat

Question 14.
What is a music?
Answer:
Music is a combination of sounds that are produced in an order and pleasant to hear.

Question 15.
What is a noise?
Answer:
The sounds which are not pleasant to hear is called a noise.

Question 16.
What is pitch?
Answer:
The shrillness of a sound is known as pitch.

Question 17.
What is frequency?
Answer:
The number of vibrations per second is called frequency.

Question 18.
What is audible sounds? What is audible range?
Answer:
The sounds that a normal human being can hear is called audible sounds. Frequency of audible sound ranges from 20 cycles / second to 20000 cycles / second.

Question 19.
Do we hear the sounds produced by bats?
Answer:
We cannot hear sounds produced by bats because the sounds produced by bats have frequency more than 20,000 cycles / seconds that is more than audible range.

Question 20.
Does the sound travel if there is no medium?
Answer:
Sound required medium for its propagation. So sound does not travel if there is no medium i.e vacuum.

Question 21.
A bird makes high pitch sound and a lion makes a low pitch roar. Which one produce sound of more frequency?
Answer:
The bird produces sound of more frequency because it has high frequnecy as we already know pitch depends upon frequency.

Question 22.
Why do we produce sounds with different pitches or amplitudes while speaking?
Answer:
The vibration in pitch and amplitude of sound during our speech helps us to communicate with others in form of language.

Question 23.
Lightning and thunder take place in the sky at the same time at the same distance from us. Lightning is seen earlier and thunder is heard later. Can you explain why?
Answer:
The speed of light is more than speed of sound so light travels faster. So we can see lightning first then we can hear thunder.

Question 24.
How intensity of sound related to its unit?
Answer:
The smallest audible sound (nearer to total silence) is 0 dB. A sound 10 times more powerful is 10 dB. A sound 100 times more powerful that of total silence is 20 dB. A sound 1000 times more powerful than sound nearer to silence is 30 dB.

Question 25.
How many times is a jet engine more powerful than the whispering sound?
Answer:
The decibel rating of jet engine = 120 dB
The decibel rating of whisper = 20 dB (for practical purpose)
The number of times a jet engine more powerful than a whisper = 1010 times
{120 – 20 = 100 that is taken as 1010}

Question 26.
How do you feel when you hear sounds in busy traffic?
Answer:
It is very unpleasant to hear.

Question 27.
How do you feel while listening to songs from a radio?
Answer:
It is very pleasant to hear.

Question 28.
Which of the above sounds are more pleasant to hear?
Answer:
Songs from radio are more pleasant to hear.

Question 29.
What is the unit to measure the sound intensity?
Answer:
Decibel is the unit for measuring the intensity of sound. It is denoted as dB.

### 8th Class Physical Science 6th Lesson Sound 2 Marks Important Questions and Answers

Question 1.
What is sound pollution? What are the causes of sound pollution?
Answer:
The unwanted sound in our surroundings is called sound pollution.
Causes of sound pollution:

1. Sounds of traffic
2. Sounds by motor bikes and their horns
3. Sounds in construction sites
4. Sounds at industries
5. Sounds at mines
6. Sounds during explosions and bursting of crackers
7. Sounds from mixer/grinder, washing machines and motors, etc.

Question 2.
Write some common sounds and their decibel ratings.
Answer:
Near total silence – 0 dB
A whisper – 15 dB
Normal conversation – 60 dB
A lawn mower – 90 dB
A car horn – 110 dB
A jet engine – 120 dB
A gun shot or fire cracker – 140 dB

Question 3.
How many times is a car horn more powerful than normal conversation?
Answer:
The decibel rating of car horn = 110 dB
The decibel rating of normal conversation = 60 dB
The number of times a car horn more powerful than normal conversation = 105 times
{110 – 60 = 50 which is taken as 105} (The explanation beyond our syllabus. It is based on logarithms)

Question 4.
How can you explain the sound has energy?
Answer:
Sound has energy: Take a plastic bottle and a cell phone.

Cut the top of the bottle so that it looks like a glass. Play songs on the mobile phone in high volume and place it in the bottle. Close the mouth of bottle with a balloon using rubber band so that it covers the bottle as shown in the figure and stretch it tightly so as to behave like a diaphragm. Place some sugar crystals or small sand particles on the balloon diaphragm and observe the movement of particles. Do the same activity after removing the phone from the bottle. Sound has energy

Question 5.
What are the differences between the noise and music? Explain.
Answer:

 Noise Music 1. Sounds which are not pleasant to hear are called Noise. 1. Sounds which are pleasant to hear are called Music. 2. Noise is an irregular combination of sounds. 2. Music is a combination of sounds. Which are produced in order. 3. It is unpleasant to hear. 3. It is pleasant to hear.

Question 6.
Explain the sources which produce sound pollution in your surroundings.
Answer:
Sources of sounds that are produce to sound pollution:

1. Sounds in traffic
2. Sounds by motor vehicles
3. Sounds in construction sites
4. Sounds in industries
5. Sounds in mines
6. Sources of sound pollution like mixer, grinder, washing machines and motors, etc.

Question 7.
What is the effect of humidity on quality of sound propagation? Is there any difference in propagation of sound in air during the summer and winter seasons? Discuss.
Answer:
With increase in humidity, density of air decreases. So with rise in humidity velocity of sound increases.
This is why sound travels in humid air (rainy season or winter) than in dry air (summer) at the same temperature.

Question 8.
Why the voice of men, women and children are different?
Answer:
The vocal cords of men about 20 mm long. In women these cords are about 5 mm shorter in respect to men. Children have very short vocal cords. That is the reason that voice of men, women and children are different.

Question 9.
On which property of vibrations does the loudness of sound depend?
Answer:
The loudness of sound is determined by its amplitude. When the amplitude of a vibration is large, the sound produced is loud. When the amplitude is small, the sound produced is feeble.

Question 10.
What are the harmful effects of noise pollution?
Answer:

1. Presence of excessive noise in the surroundings may cause many health related problems.
2. Lack of sleep, hypertension (high blood pressure), anxiety and many more health disorder may be caused by noise pollution. A person who is exposed to a loud sound continuously may get temperory or even permanent deafness.

Question 11.
What is the effect of humidity on quality of sound propagation? Is there any difference in propagation of sound in air during the summer and winter seasons? Discuss.
Answer:
In the winter season the air has fogs and behaves as liquid medium. So, the air moves little faster in it. Whereas in the summer the air is dried and no possibility of droplets. Hence the sound moves slower.
The propagation of sound is Solids > liquids > gases

Question 12.
Define audible sounds and inaudible sounds.
Answer:
Audible sounds:
The sounds that a normal human being can listen are called audible sounds. Frequency range is 20 cycles/sec – 20000 cycles/sec.
Inaudible sounds:
The sounds that a normal human being can’t listen are called inaudible sounds. Frequency range is less than 20 cycles/sec. or greater than 20000 cycles/sec.

### 8th Class Physical Science 6th Lesson Sound 4 Marks Important Questions and Answers

Question 1.
Describe structure of larynx or voice box.
Answer:
Larynx is the important organ in human body to produce sound. It has two muscular ligaments at the end of wind pipe called vocal cords. They are stretched across voice box, it leads to a narrow slit between them, to allow passage of air.

Vocal cords open during breathing to allow air into lungs. Vocal cords close when we speak.
The air from the lungs presses between them to use vibration and produce sound.

Question 2.
Draw anatomy of the larynx and label its parts.
Answer:

Question 3.
Draw the figures of using three musical instruments in your surroundings.
Answer:

Question 4.
a) Can sound travel in vacuum? Explain.
b) In which medium sound travels much faster and slower? Give some examples.
Answer:
a) Sound can’t travel in vacuum as it needs particles for propagation. As vacuum is empty, it is not possible.
b) Sound travels much faster in solids as the particles in solids are very closely packed, e.g.: Sound travels in train tracks (Railway tracks).
Sound travels much slower in gases as the particles in gases (air) are very loosely packed.
e.g.: Thunder or sound produced from amplifier at a long distance is feeble to hear.

Question 5.
Which object is vibrating when the following sounds are produced?
i) The sound of sitar or veena
ii) The sound of tabla
iii) The buzzing of bee or a mosquito
iv) The sound of a school bell
v) The sound of bursting balloon
vi) The radio
Answer:
i) Strings of sitar or veena vibrate to produce sound.
ii) The skin of the tabla vibrate to produce sound.
iii) Wings of mosquito or a bee vibrate to produce sound.
iv) The disc of the bell when beated with hammer vibrate to produce sound.
v) Air vibrates to produce sound.
vi) In the radio speakers vibrate to produce sound.

Question 6.
On which property of vibrations determines the pitch of the sound? Explain with examples.
Answer:

1. The frequency determines the shrillness or pitch of sound.
2. If the frequency of vibration is higher we say that the sound has a higher pitch.
3. If the frequency of vibration is lower, we say that the sound has a lower pitch. For example, the drum vibrates with a low frequency. Therefore, it produces a low pitched sound:
4. On the other hand, a wristle has a higher frequency, and therefore produces a sound of higher pitch.
5. A bird makes a high pitched sound whereas a lion makes a low pitch roar.

Question 7.
How can the noise pollution be controlled in a residential area?
Answer:

1. The noisy operations must be conducted away from any residential area.
2. Noise producing industries should be set up away from such areas.
3. Use of automobile horns are minimized.
4. T.V and music systems should be run at lower volumes.
5. Plants must be planted along the roads and around buildings to minimize the harmful effects of noise pollution.

Question 8.
What is the audiable range of frequencies for human beings? Explain.
Answer:

1. Sound of frequencies less than about 20 vibrations per second (20 Hz) cannot be detected by the human ear.
2. Such sounds are called inaudible.
3. On the other side, sound of frequencies more than about 20,000 vibrations per second (20,000 Hz) are also not audible to the human ears.
4. Thus for human ears, the range of audible frequencies is roughly between 20 to 20,000 Hz.

Question 9.
What is eardrum? How does it play an important role in hearings?
Answer:

1. We hear sound through our ears.
2. The shape of the outer part of ear is like a funnel.
3. When sound enters in it, it travels down a canal at the end of which a thin membrane is stritched tightly.
4. It is called the eardrum.
5. It performs an important function.

### 8th Class Physical Science 6th Lesson Sound Important Questions and Answers

Question 1.
Majority of communication in human beings is through speech. Name the organs which give human beings the ability to talk.
Answer:

1. Vocal cords
2. Lips
3. Teeth and tongue
4. Nose and throat

Question 2.
Why our steps do not produce sound if we walk on a carpet floor?
Answer:
Carpets are soft and as we know soft materials are bad conductors of sound. Thus the
carpet tends to absorb the sound produced. Also when we walk on the carpet the amplitude and vibrations of the floor is reduced leading to a lesser sound.

Question 3.
Sound does NOT travel in vacuum. Explain why.
Answer:

1. Sound energy travels in the form of wave.
2. To produce waves medium is required.
3. Hence, if there is no medium, sound waves cannot form.

Question 4.
Complete the following table.

 Vibrating part of instrument Name of the instrument Stretched membrane Stretched string

Answer:

 Vibrating part of instrument Name of the instrument Stretched membrane Tabala, Dappu, Mrudangam Stretched string Veena, Guitar, Violin

Question 5.
Mention the sounds which are responsible for sound pollution. Suggest four controlling measures of sound pollution.
Answer:
Causes of sound pollution:

1. Sounds of traffic
2. Sounds by motor bikes and their horns
3. Sounds in construction sites
4. Sounds at industries
5. Sounds at mines
6. Sounds during explosions and bursting of crackers
7. Sounds from mixer / grinder, washing machines and motors etc.

The steps to reduce sound pollution :

1. Attach silencers to the bikes and other machines to reduce sound.
2. Manufacture machines that work with lesser noise.
3. During the use of TVs and taperecorders tune down volume of sound.
4. Plant trees to reduce sound pollution.

Question 6.
What is sound pollution? Write effects of sound pollution. Suggest some measures to control sould pollution.
Answer:
The unwanted sound in our surroundings is called sound pollution.
Effects of sound pollution on bio-diversity:

1. The first harmful effect is loss of hearing.
2. It also leads to several health related problems, e.g : Sleeplessness, hypertension, increase in blood pressure, etc.
3. It effects the mental health of people.
4. In animals, noise can increase the risk of death by altering predator or prey detection and avoidance, interfere with reproduction and navigation and contribute to permanent hearing loss.
5. Noise pollution causes poor quality of crops.
6. Under water animals such as whales and dolphins too experience discomfort due to noise pollution caused by submarines, shipping companies and sonars. Cuttle fish and octopus suffer serious damage from noise pollution.

The steps to reduce sound pollution :

1. Attach silencers to the bikes and other machines to reduce sound.
2. Manufacture machines that work with lesser noise.
3. During the use of TVs and taperecorders tune down volume of sound.
4. Plant trees to reduce sound pollution.

Question 7.
Kushwanth said “Vibrating objects produce sound.” Establish that the given statement is true with relevant example from your surroundings.
Answer:
The statement given by Kushwanth is correct.
That is “vibrating objects produce sound”.
1. Eg: 1) If we ring the bell in the school, sound will produce.
2) If we touch the bell while ringing, vibrations will experience.

2. Eg: 1) We can observe sound coming from the engine of a vehicle.
2) This is due to vibration of the engine.

3. Eg: 1) Musical instruments vibrates and produce sound.
2) If we pull the string of a veena or guitar.
3) It will produce sound.

Question 8.
Based on the below information answer the following questions.

 Musical Instrument Vibrating part producing sounds Veena Stretchings string Tabla Stretched membrane Flute Air Column Dholak Stretched membrane Sitar Stretching string Drum Stretched membrane

a) Name the instruments which have vibrating part like a thin elastic rubber band.
Answer:
Tabla, Dholak, Drum.

b) What are the vibrating particles in the air column?
Answer:
Air particles.

c) What is the difference between Tabla and Sitar in terms of how they produce sound?
Answer:
In Tabla, stretched membrane vibrates and produce sound. Whereas in Sitar stretching string vibrates and produce sound.

d) How to produce different frequencies using a flute?
Answer:
By closing holes of the flute with fingers (or) By changing length of the air column.

Question 9.
Write about the propagation of sound in different media.
Answer:

1. Sound produced by source travels in a medium in the form of waves.
2. Vibrations produced by source of sound travel by particles of medium.
3. In the case of solids, particles of solid substance vibrates and travel along the substance.
4. In the case liquids, molecules of liquids carry the vibrations for sound propagation.
5. In the case of gas, gaseous molecules act as carries of vibrations and allow the sound propagation.

Question 10.
Explain the structure and functions of the ear using a diagram.
(OR)
Describe briefly about structure and functioning of the eardrum.
Answer:
Our ear consists of three sections, the outer ear, the middle ear and the inner ear, Pinna of external ear collects the sound vibrations. They enter into the ear canal. We have learnt that sound travels in the form of vibrations: These vibrations strike the tympanum (eardrum) and make it to vibrate.

The vibrations from the tympanic membrane reach the middle ear (ear ossicles), contains three small bones malleus (hammer shaped), incus (anvil shaped) and stapes (stirrup shaped). They magnify the sound vibrations.
The stapes transmits the vibrations to the membrane of oval window. The oval window has the surface area 1/20th of the ear-drum. By this the vibrations increase 30 to 60 times. The vibrations from the oval window transmit to the cochlea which is the inner part of the ear. The cochlea is filled with fluid which transmits the vibrations. The motion of the vibrations in the cochlea is detected by tiny hairs connected to nerves at this point. The vibrations are transformed into electrical signals and carried by the nerves to the brain where the sensation of the sound is realized.