Give reasons for the following.
1. How is it possible to see the shadow of a flying bird on the ground?
2. How does the size of the shadow of an object change when its distance from the
screen decreases?
3. Why is a lunar eclipse not equally visible from different parts of the earth?
4. Why does a lunar eclipse last for a much longer duration as compared to a
solar eclipse?
5. To obtain a larger image while using a pinhole camera, the distance of the object
from the pinhole must be small, or, the distance of the image from the pinhole must
be large. Which is a better option and why?
Answers
Answer:
1) Birds flying high in the sky do cast their shadow but because they are shading an area that is very tiny, the shadow is not visible. The higher the bird flies, the smaller the shadow it casts
1. Birds flying high in the sky do cast their shadow because they are shading an area that is very tiny, the shadow is not visible. The higher the bird flies the smaller the shadow it casts.
2. Thus, between the points on the object and points on the screen there is one to one coordination. If we decrease the distance between the source of light and the object then the size of the shadow will increase because the amount of light falling on the screen will decrease.
3. The moon moves over the sun during the day and it becomes dark as the sunlight gets blocked.
Since Moon is smaller as compared to Sun and Earth, it's shadow on Earth isn't very big.
4. Duration of eclipse mainly depends upon the time the moon takes to move out of light way. In lunar eclipse the moon takes more time to move, while on solar eclipse the moon takes lesser time. So lunar eclipse is longer than solar eclipse.
5. I don't know the answer.