How does a black light work?

looney_tunes

A black light actually produces ultraviolet light, which the human eye does not detect. When UV light hits a phosphor, the phosphor absorbs it, and converts the energy into visible light, making it appear to glow. I recall a demonstration from primary school in which the room was darkened, and all of our (white uniform) shirts glowed. "White T-shirts and socks normally glow under a black light because modern detergents contain phosphors that convert UV light into white light. This makes whites look "whiter than white" in normal sunlight. What you are seeing in sunlight is the normal reflection of visible white light from the cloth, as well as the emission of white light that the phosphors create from UV light in sunlight. The T-shirt really is whiter than white!" http://science.howstuffworks.com/black-light.htm Sep 24 09, 2:46 AM