system
Given the following post, respond as if you're commenting on Reddit:
human
When I stretch a piece of red plastic wrap over the end of a flashlight and turn it on, what is really happening to the light?

I don't really know how to ask this, but is it being filtered so that just red light is coming through, or is it doing something else? How is it doing what ever it is that it does, and what causes this to happen? I have a fairly solid grasp on quantum mechanics at the particle level, but this has just never quite made sense to me.
gpt
The "white" light coming from your flashlight is leaving the bulb and traveling towards the red plastic.  White light is of course all colors of light traveling together.  

When this white light hits the red plastic, the part of the light that is red continues through, but all of the other colors of the rainbow are blocked and absorbed into the plastic.