AP State Syllabus AP Board 8th Class Physical Science Important Questions Chapter 12 Stars and the Solar System
AP State Syllabus 8th Class Physical Science Important Questions 12th Lesson Stars and the Solar System
8th Class Physical Science 12th Lesson Stars and the Solar System 1 Mark Important Questions and Answers
What is Dakshinayanam and Uttarayanam?
When the sun looks like travelling towards south of the sky, it is called Dakshinayanam. When the sun looks like travelling towards north of the sky it is called the Uttarayanam.
What is a sundial?
A clock based on shadows of an object due to sunlight is called sundial.
What are phases of the moon?
The changes in appearance of moon are called phases of the moon.
Why does solar eclipse occurs only on a new moon day?
A solar eclipse happens when moon passes between the earth and sun, causing people on earth to be completely or partially unable to see the sun, because the moon is in the way that is possible only on new moon day.
What are the spots on the moon?
The black spots on moon are creators of different size which on seeing from earth appear as black spots during full moon day.
What are stars?
The self luminous bodies which emit light and heat in the sky are called stars.
What are constellations?
The group of stars which appear in the shape of animals or human beings are called constellations.
What is a galaxy? Our sun belongs to which galaxy?
A group of stars which contains millions of stars are called galaxy. Our sun belongs to Milky way galaxy.
Which makes our universe?
Millions of galaxies together makes our universe.
What is the solar system?
The sun and the celestial bodies which revolve around it form the solar system. It consists of large number of bodies such as planets, comets, asteroids and meteors.
Why planets are revolves around the sun?
The planets are revolving around sun because of gravitational attraction between the sun and planets.
What is period of revolution? How does it vary?
The time taken by a planet to complete one revolution around sun is called period of revolution. As the distance of the planet from the sun increases period of revolution increases.
What is period of rotation?
The time taken by a planet to complete one rotation is called period of rotation.
What is satellite? What is natural satellite of earth?
Any celestial body revolving around another celestial body is called its satellite.
The natural satellite of earth is moon.
The earth is revolves around the sun. Does it make earth a satellite of the sun?
The earth can be said to be a satellite of the sun, though generally we call it a planet of sun. We use the term satellite for the bodies revolving around planets.
What are artificial satellites?
There are many man made satellites revolving round the earth. These are called artificial satellites.
Does the sun rise in the east on Venus? If the answer is no what is the reason?
No, the reason is Venus rotates from east to west. So, on Venus the sun rises on west.
Why Mars is called red planet?
Mars is called red planet because the breakdown of iron rich rocks creates a rusty dust on the planet.
How earth appears from space?
The earth appears blue green due to the reflection of light from water and Iandmass on its surface.
What are the planets which revolve from east to west?
Venus and Uranus are two planets which revolve from east to west.
What are asteroids? Where does they present?
Small objects revolve around the sun are called asteroids. They are present between Mars and Jupiter.
What is Halley? When does it last appear? Can you tell when Halley visible again?
Halley is a comet, which is periodically appear for every 76 years. I was last seen in 1986. It will visible once again in the year 2062.
What are the artificial satellites launched by India?
Aryabhatta, INSAT, IRS, Kalpana-I, EDUSAT, etc. are some satellites launched by India.
Why Pluto is not consider as a planet?
International Astronomical Union (IAU) decided that Pluto was no more a planet because it does not follow the rule of “cleared the neighbourhood.” That means sometimes it is entering into orbit of Neptune.
What is an orbit?
A planet has a definite path in which it revolve around the sun. This path is called an orbit.
8th Class Physical Science 12th Lesson Stars and the Solar System 2 Marks Important Questions and Answers
Write briefly about sun.
- The sun is the nearest star to us.
- It is continuously emitting huge amounts of heat and light and other electromagnetic radiations.
- The sun is the source of almost all energy on the earth.
- In fact, the sun is the main source of heat and light for all planets of our solar system.
What are planets? Why they appear brightly than stars?
- The big steady bodies shining more brightly than stars in the clear sky are called planets.
- They are not self luminous like stars. They appear brightly because they just act like mirrors and reflecting the sun light and heat falling on them.
What are the motions of planets?
Every planet has two types of motion.
- Revolution motion: Moving around the sun.
- Rotation motion: Moving around an axis passing through it.
Why earth is only planet on which life known to exist?
- Earth is only planet on which life exists in the solar system the reason is some environmental conditions are responsible for the existence and continuation of life on the earth.
- These include just the right distance from the sun so that it has right temperature range, the presence of water and suitable atmosphere and a blanket of ozone.
What are comets? Write briefly about comets.
- Comets are members of our solar system.
- They revolve around the sun in highly elliptical orbits.
- A comet appears generally as a bright head with a long tail.
- The length of the tail grows in size as it approches the sun.
- The tail of comet always directed away from the sun.
- Their period of revolution round the sun is usually very long. Many comets are known to appear periodically.
Why does pole star seem to be stationary?
The Pole Star is situated in the direction of the earth’s axis and that is why it does not appear to move even though all stars appear that they are moving because of the rotation of earth. So the pole star seems to be stationary.
What factors to be taken into consideration to view the pole star at your place?
The position of pole star is fixed and does not change.
a) We can locate the pole star with the help of two constellations Great bear and Cassiopeia.
b) If you are able to spot only the Great bear look at the two stars that form the outer side of rectangular head.
c) Extend the imaginary line from these two stars.
d) Pole star will be located on that extended line with a distance about 5 times the distance between the two stars.
e) If only Cassiopeia is visible, the pole star will be located on the line extended from the middle star.
Name the periodic comet. Why is it so called?
- Halley’s comet is periodic comet. It is called periodic comet because it appears after regular interval of time.
- A comet is visible only when it approches the sun because the sun’s rays makes the gas glow.
- Halley’s comet has a period of 76 years i.e., it is seen after every 76 years.
What do you mean by remote sensing satellite?
- It is the acquisition of information about an object or phenomenon without making physical contact with the object.
- It is generally the use of aerial sensor technologies to detect and classify objects on the earth by means of propagated signals.
Why are meteors commonly called shooting stars?
- When meteor enters the atmosphere of the earth at high speeds, these are heated up.
- The heat produced is so high and the meteors start glowing and eventually evaporated within a short period of time.
- The growing meteor bursts leaving behind a streaks of light. Therefore they are called shooting stars.
How does the motions of a satellite differ from a planet?
A satellite revolve around same planet in a fixed orbit while a planet revolves around the sun in a fixed orbit. Planets revolve faster than satellites.
8th Class Physical Science 12th Lesson Stars and the Solar System 4 Marks Important Questions and Answers
When does a solar eclipse occurs? Explain different types of solar eclipse.
A solar eclipse occurs when the shadow of the moon falls on the earth. It occurs only on new moon day.
Types of solar eclipse:
- Total solar eclipse: It occurs when the moon completely covers the sun, as seen from earth.
- Partial solar eclipse: It can be observed when only the partially shaded out region of the shadow cast by moon (Lunar penumbra) touches the earth.
- Annular eclipse: It occurs when the moon appears smaller than the sun as it passes centrally across the solar disk and a bright ring, or annulus, of sunlight remains visible during eclipse.
- Hybrid eclipses: These are a rare form of solar eclipse, which changes from an annular to a total solar eclipse along its path.
When does a lunar eclipse occurs? Explain different types of lunar eclipses.
Answer: A Lunar eclipse occurs when the shadow of the earth falls on the moon. It occurs only on full moon day.
Types of Lunar Eclipse:
- Total lunar eclipse: It occurs when the earth’s shadow (umbra) obscures all of the moon’s visible surface.
- Partial lunar eclipse: It can be observed only when part of the moon’s visible surface is obscured by the earth’s shadow.
- Penumbral lunar eclipse: It happens when the moon travels through the partially shaded outer region of the shadow cast by the earth (earth’s penumbra).
Write an activity to show how path of sun and moon changes during solar eclipse.
Make two discs one white and one black of the size of sun and moon in figure.
We shall now find the centres of the sun and moon at each stage. To do this take the white disc we have made and place it exactly on the white portion of any of the stages of diagram.
Pierce a hole through the centre of white with a pin to mark the spot at the centre of the sun’s position at that stage in the diagram. Remove the white disc and mark the spot with the pencil.
In this way, mark the sun’s centre at every stage of the eclipse in diagram. Join the spots with a line. This line depicts the path of the sun.
To find the moon path, repeat the exercise, but this time use the black disk and mark the centres of the black portions at each stage of the eclipse. Join these spots with a line and we will get the path of moon during the eclipse.
Write briefly about meteors.
- At night, when the sky is clear and the moon is not visible we may sometimes see bright streaks of the light in the sky.
- These are commonly known as shooting stars.
- They are not stars, they are meteors.
- A meteor is a small object that occasionally enters the earth’s atmosphere.
- It has a very high speed.
- The friction due to atmosphere heats it up.
- It glows and evaporates quickly.
- That is why the bright streak lasts for a very short time.
- Some meteors are large and so they can reach the earth before they evaporate completely.
How people came to an understanding that earth is spherical?
In olden days people felt that earth is flat because it looks flat. However they had a doubt, if it is flat how does the water in ocean remain there, Why does it not spell out of the earth ? To get clarity they assumed fencing around flat earth. After that,
- they assumed shape of earth is round by observing the shadow of earth in lunar eclipse. In every eclipse they found the shape of the earth is in round even though there is a chance of getting linear, elliptical shadows by a circular object.
- some sailors who started their journey in ocean, reached the same place after travelling large distance in one direction only.
- observing ships approaching the port also helped to change their opinion about the shape of the earth, that is, usually they see smoke of the ship first and then top of the ship after that the whole ship.
- observations about the movement of stars. Different stars visible from different places on the earth also helped to think about the shape of the earth.
- in 1969 when man landed on the moon and observed the earth’s shape from the moon and it is spherical.
How does people came to an understanding that earth rotates on its own axis?
Answer: People from olden days thought that earth is located in the centre of the universe with sun, moon and stars moving around it. They also thought that sun, moon and stars are located on transparent concentric spheres surrounding the earth, because they are not falling down.
The three spheres are rotating on their axis from east to west that is why sun, moon and stars appear to revolve from east to west around the earth. They also assumed that the shpere on which sun is located rotates east to west and oscillate from south to north that is why Uttarayanam and Dakshinayanam are happening.
Because of the uneven movement of some stars (actually they are planets) which they observed, it is very difficult to explain model of universe which required so many transparent spheres around earth. Nicholas Copernicus suggested that sun is at the centre of universe and all other celestial objects are revolving around the sun from west to east. It was assumed that earth rotates on its axis. This model explain the occurence of day and night.
In this way people came to an understanding that earth rotates on its axis.
Conduct an experiment to find out the local noon time of your village/town.
- Take a stick which is a little over a meter long and fix vertically in the ground.
- Make your first observation at nine in the morning. Make a mark with a nail or peg at the point where the tip of the shadow falls on the ground. Measure the length of the shadow.
- Then make similar observations for every half an hour throughout the day till four in the evening.
- Use a clock to fix the time for making your observations.
- Enter the measurements of the length of the shadow and the time of measurement in a table making two columns, one for time and other for length of shadow.
- Find the time when the shortest show occurs.
- That gives the local noon time at that place.
Collect the information what the Chandrayaan-I brought the information from the Moon through news papers, magazines.
Our country launched Chandrayan -1 (Satellite to moon) on 22nd October 2008 to know about the moon.
The objectives of Chandrayan -1 are:
- To check the possibility of finding water on the moon.
- Finding out the elements of matter on moon.
- To search for Helium – 3.
- To make 3 – dimensional atlas of the moon.
- To study about the evolution of the solar system.
Now India is one of the six countries which have sent satellites to the moon.
What are Asteroids? Name the largest sun asteroid.
- There are small lumps of rocks orbiting round the Sun between Jupiter and Mars. They are considered to be remains of a much larger planet which broken up due to gravitational effect of jupiter.
- They are small in size.
- The size of an asteroid may vary from a kilometer to a few hundred kilometers.
- Ceres is the largest known asteroid.
- Its diameter is 633 km and it was discovered in 1801.
- There are about 1,00,000 asteriods.
What is the difference between meteor and meteorite?
a) Meteor: Meteors are stony or metallic bodies of very small size, travelling in interplanetary space and become visible when they travel through the earth’s surface. The meteors are also called shooting stars.
b) Meteorite: While travelling through the earth’s atmosphere, these fast moving bodies (meteors) get heated up to a very high temperature by air friction. The heat produced is so high that the meteor starts glowing and then burnt last. The very large meteors are able to survive from such heat destruction and actually reach the earth’s surface. These meteors are called meteorites.