Question

 You have to cast the shadow of your pencil on them with the help of a candle in a dark room. How can I obtain a shadow smaller in size than the pencil? [You cannot use mirrors or lenses and assume the candle to be a point source of light.]
A. Keep the pencil close to the wall
B. Bring the pencil closer to the candle
C. Keep the pencil the midway between the candle and the wall
D. You cannot obtain a shadow smaller than the size of pencil

Answer 1

HintThe closer an object is to the light source, the larger the shadow it casts. This is because an object closer to the source will block a larger area of the light, increasing its shadow size.

Complete step-by-step solution:Before you could change the size of the shadow you needed to generate it first. You probably didn’t see a shadow when you placed the pencil next to the flashlight and not directly into its path of light. This is because light travels in a straight line and, because the pencil was not located in the direct light path, it could not block the light from its candle.
Once you placed the pencil directly in the path, however, you should have seen a shadow on the wall that had the same shape as the pencil. This time the opaque object was able to block the light from the candle, creating the dark shadow on the wall.
Here, we are using pencil as our opaque object and candle as a source of light. You should have observed the shadow’s size decrease when you moved the pencil farther from the candle as you block less portion of light from the candle and shadow’s size increase when you moved it closer as you block a much larger portion of the light from the source when your object is closer, which increases the size of the shadow.

Hence, we can obtain the shadow smaller in size than the pencil by keeping the pencil away from the candle and keeping close to the wall. Therefore, the correct answer is A.

Note:-
Shadows are formed when an opaque object comes in the path of light. Opaque objects do not allow light to pass through them. Light travels in a straight line.