A student had a ball, a screen and a torch in working condition. He tried to form a shadow of the ball on the screen by placing them at different positions. Sometimes the shadow was not obtained. Explain.

Question

A student had a ball, a screen and a torch in working condition. He tried to form a shadow of the ball on the screen by placing them at different positions. Sometimes the shadow was not obtained. Explain.

Philoid · Accepted Answer

Some reasons due to which the shadow cannot be obtained are as follows.

1. When the screen is placed far away from the ball than he cannot get shadow on the screen.

2. The beam of light from the torch is falling parallel to the screen on the ball due to which the ball is not able to obstruct the whole light from the torch and shadow is not obtained.

3. The torch is kept away from the ball. This makes the source of light far away hence the sufficient light is not reached to the ball.

An accurate shadow of the ball will be formed only when the ball, torch, and screen are in the same straight line. The figure below shows the arrangement.