How exaclty does a black light work
I assume you are asking about how a black light source generates ultraviolet light. The principal is the same as for all flourescent lights. Ionized gas inside the bulb is excited by the current passing through it and it emits photons. Phosphorescent material inside the surface of the flourescent bulb is excited by the high energy photons striking from the inside. The photons push the electrons in the phosphor into higher orbits temporarily. These electrons subsequently emit photons at specific frequencies as they fall back into the orbits from which they came. The phosphor material is selected for the frequencies it produces. Hence the different colors or warmth of flourescent bulbs and in the case of black lights primarily ultraviolet and violet colors are produced. If you were asking about how the black light makes things glow, it is exactly the same principal of phosphorescence, but the other way around. The high energy photons from the ultraviolet lamp strike phosphors that are added to laundry detergent hat never quite rinses from your clothes. Those phosphors then glow in the blue-white range. The effect of the detergents is intentional and makes the clothes look brighter in the sun (which has ultraviolet in its spectrum) or under other bright lights.
You have probably seen black lights at amusement parts, science museums and Halloween displays. Black lights may look just like normal fluorescent lamps or incandescent light bulbs, but they do something completely different. Switch one on, and white clothes, teeth and various other things glow in the dark. For example, if you have a fluorescent poster and shine a black light on it in a dark room, the poster will glow brightly. You may have also seen pieces of paper that look blank in regular light but spell out a glowing message under a black light. Many amusement parks use hand stamps that are invisible until you view them under black light. In this article, we'll find out exactly what's going on here. We'll also see why black lights make some objects glow but not others, and we'll look at some interesting black light applications. you can read more..it's accessible on the website below
A fluorescent tube contains a plasma with current flowing through it. That gives off ultraviolet light which strikes a fluorescent coating on the inside of the tube wall A fluorescent material is one which gives off photons of lower energy when illuminated by, in this case, UV light. The secondary light in regular tubes is visible, but for black lights it's UV (like the plasma light). Many other materials lying around (shirts, paints, teeth) are fluorescent when exposed to (invisible) UV, and they give off visible light too.
They work just like any other light. They just emit photons of a different energy (wavelength). Black lights bulbs emit ultraviolet light, which is light waves less than 380nm in length, while regular bulbs emit visible light waves, which is between 380 and 780 nm in length.
