Optics
The science of making light go where we want it to is called optics.

The simplest optical phenomenon is a shadow, in which some of the rays of light are blocked by an object. We get big shadows if the object is much closer to the light source than it is to the wall where the shadow appears.



 


We get sharp shadows if the light source is small compared to the other distances involved.



Here's an example


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Warning: Don't Look At the Sun