Class Notes NCERT Solutions for CBSE Students
Question: What do you mean by ‘phases of the Moon’? Draw a labelled diagram to show the phases of the Moon.
Answer: The moon’s revolution and rotation are such that only one side of the moon always faces us. Also, we can see that portion of this side which reflects sunlight to us. This changes every day as the relative positions of the sun, earth and moon change every day. These are explained here.
New moon: When we do not see the moon at all.
Crescent moon: We see only a part of the moon
First quarter: When we see half of the moon
Gibbous moon: When we see more than half of the moon
Full moon: When we see the full moon. Then the cycle reverses.
These shapes of the bright part of the moon, as seen from the earth, are known as phases of the moon.
Question: Why can’t we see stars during the day?
Answer: Due to the brightness of the sun during the day we cannot see stars at that time.
Question: Suppose a star which is 100 light years away explodes today. It is highly unlikely that you will be able to see the explosion. Why?
Answer: It is highly unlikely that a person alive today lives to see the exploding star as light from the star will take 100 years to reach the earth.
