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Katie Frost

Page history last edited by kafr 11 years, 2 months ago

How Black Lights Work



What exactly is a "black light"?


     Black lights may look just like normal incandescent lights, but they do something completely different. Going under a black light would make white clothes, and even your teeth, glow in the dark! When turning on a black light in a dark room, what you will see is a purplish glow. But a black light produces an ultraviolet light which we cannot see. Our eyes can see visible light in a spectrum, ranging from red to violet. Above visible light is ultraviolet light, which is why we cannot see it.



Visible light frequencies



How does a black light work?


     The way a black light works is very similar to the way a flourescent tube light works. Electricity is channeled through a tube filled with inert gas and a small amount of mercury to produce light. The mercury is charged by the electricity, causing it to release photons of light. Since the majority of the light produced is UV light, a molecular change takes place for it to emit a more sufficient light. For this to happen, the outer tube is coated with phosphorus. When the UV light hits the phosphorus, it heats up. When it cools, it releases a photon of visible light. The phosphorus coating is designed to absorb the dangerous UV-B and UV-C rays, allowing only the safe UV-A rays to escape.
























Comments (2)

zavi said

at 11:56 am on Dec 11, 2009

whats up katie?

Bill Briggs said

at 12:21 pm on Dec 17, 2009

Looks good so far. Make sure you include a couple pictures of a black light, or what things look like under one. If you can find a diagram of how one works, that would be good, also.

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