You hold your hand 3 feet above the ground and look at the shadiw cast by the sun. You repeat this inside using the light from a 2-foot by 4-foot fluorescent light boxin the ceiling. In which case will the penumbra be more pronounced?

1 Answer
Aug 7, 2018

In the case of the fluorescent light boxin the ceiling.


Light rays that are not parallel are the cause of a penumbra. The light rays from the sun are (nearly) parallel due to the long distance they have traveled . When your hand is hit by the rays from the light in the ceiling, light comes from all parts of the light to hit any single spot on your hand.

I hope this helps,