[justinpombrio]

LCD screens are really cool! My dad had a half-broken one at some point, and we peeled the outer layer partly off. It was pure white underneath. Just constant white light, no matter what was being displayed.

But if you looked at the pure white with polarized sunglasses, you could see the image! The pixels don't turn on and off, they just change polarization. And there's a thin layer that blocks light of one polarization, but not the other.

EDIT: Wikipedia has a picture. https://en.wikipedia.org/wiki/Liquid-crystal_display#/media/...