Black Light

One of the interesting questions I've had about the physics of light is about black light. It always interests me going to Hinkle Family Fun Center and Nickel city where you go down the hallway, and white clothing glows in the dark. My dad told me about black light posters he used to have back in the 1970's too. So I looked up online how a black light works and here's what I found:

So, a black light is one that produces light that is outside the narrow range of visible light. A black light produces Ultra-voilet light that the human eye can't see. The reason white shirts glow in the dark is because modern detergents contain phosphors that emit visible light when it reacts to radiation from UV light from black lights. Black lights usually come in two forms: a tube black light and an incandescent light bulb. They both work the same way: the black glass absorbs all light waves besides the UV-A and some blue or voilet visible light because of the special phosphor coating on them.

http://science.howstuffworks.com/innovation/everyday-innovations/black-light.htm