USV-C

USV-C

(alt-text)

Ultra-Serial Violet C light is unpolarized, so you don't have to flip the polarizing filter over when you get the orientation wrong the first time.

What If? is now on YouTube!
Check out the first video for the answer to
“What if we aimed the Hubble Telescope at Earth?”
and follow xkcd’s What If? The Video Series channel to be notified about each new video.