Question

The size of the visible part of the Moon, after the full moon day till the new moon day.

• A. Eemains the same
• B. Increases
• C. Decreases
• D. Either increases or decreases

Answer 1

Answer: (C)

Decreases

The moon revolves around the Earth from East to West. Along with the Earth, it also revolves around the Sun. Moon does not have its own light. Hence, we can see only that part of the moon that is illuminated by the Sun. When the moon is in the East, it lies somewhere between the Earth and the Sun. Thus the illuminated part faces the Sun and the dark part faces the Earth. Thus we cannot see any moon in the sky. This is the new moon day. After this, gradually the Moon starts moving towards the West through North. As it moves in this path, the illuminated part of the Moon gradually faces the Earth and we see the phases of the Moon from the new moon, to the crescent moon. Then half-moon, and finally the full moon, when it reaches the West, in the West, the entire illuminated part of the moon faces the Earth and it is the full moon day. Then the moon gradually starts moving towards the east once again through south and the visible part of the moon goes on decreasing in the same manner until the new moon day and the cycle keeps repeating itself. Thus we see the phases of the Moon. It takes 15 days for the moon from new moon day to full moon day and another 15 days from full moon day to new moon day.