NCERT Solutions for Class 4th The World Around Us Chapter 10 Shapes of the Moon — Discuss
Book page 160 Updated on2026-09-19
Q1.
Is there a pattern to the way the shape of the Moon changes?
Answer
Yes, there is. The shape changes in a fixed order, and then the order repeats.
A night with no Moon at all — Amavasya.
Then a thin shape like the letter ‘C’.
Then it looks as if it has been cut down the middle.
Then almost round, and then a complete circle — Poornima.
After that it gets thinner again, night by night, till there is no Moon once more.
The order in which the Moon’s shape changes, night after night.
So the pattern is: thin → half → full → half → thin → not visible → and it all begins again.
Why this matters: Because the pattern repeats in the same way every time, people could count days with it. That is how the earliest calendars began, long before clocks and printed calendars.
Check it yourself: Look at an Indian calendar at home. Poornima and Amavasya are marked on it, and they come back again and again, with the same number of days in between.
Q2.
Are there days when the Moon is not visible in the sky?
Answer
Yes. There are nights when the Moon is not visible at all.
Such a night is called Amavasya, or the new Moon.
It happens periodically — that is, it comes back again after the same number of days, every time.
Diwali is celebrated on the day when there is no Moon in the sky. That is why we light so many lamps.
Eid is celebrated on the day the Moon is seen on the first night after a New Moon.
Why we should be careful: A cloudy night is not Amavasya. On a cloudy night the Moon is there but hidden behind the clouds. On Amavasya the sky may be perfectly clear and there is still no Moon.