Black Lights – How They Glow
Posted By Houston Decorator on August 19, 2010
One of the many things in life that seems to fade away when a person enter adulthood alongside cotton candy and candy necklaces would have to be black lights. This kind of lighting is usually only significant for a few school dances in junior high, but how they work is pretty interesting for anyone who thinks learning is a lifetime pursuit.
Most of us have been introduced to the light spectrum at some point, but we will refresh in case 7th grade science was some time ago.
The spectrum goes as follow:
Radio – Microwave – Infrared – Visible – Ultraviolet – X-Ray – Gamma Ray
These waves go from long wave length to short and as humans we can only see the waves in the middle of the spectrum, appropriately labeled “visible”. Within the “visible” section we can see light in the different colors: red, orange, yellow, green, blue, violet. After violet we hit ultraviolet light which our eyes cannot see.
Why the lengthy, and probably a bit dull explanation you are asking? Simply so that we can all completely understand the next statement-
Black lights produce ultraviolet light, which we cannot see. However, we can see a glowing purple sometimes, which makes perfect sense because it is just a step below on the light spectrum.
But the waves that we cannot see coming out of the black light really isn’t what makes them special; it is the way they make everything in the vicinity seem to glow. What we see glowing is actually any substance that emits light when it is hit with some sort of radiation, this is known as a phosphor.
Many things are a phosphor. Natural phosphors include teeth and fingernails and some manmade materials with phosphors include some fabrics (think of the glowing white cool t shirts for men), highlighters and television screens.
Black lights are available in two bulb types – one like the traditional incandescent bulb and another like a CFL.
The tubular shaped bulb is like a CFL light becauseit is filled with an inert gas and a bit of mercury, but the phosphor coating is different from a traditional CFL in that the one used in a black light soaks up dangerous waves and only emits ultraviolet light to shine (and a little bit of violet sometimes).
The black light that is basically just an incandescent includes a light filter which absorbs everything the filament emits except the ultraviolet light.
So there you have it: two pretty typical bulbs, CFLs and incandescents, jimmy-rigged a bit to release only ultraviolet light and we have black light ready to make phosphors out there glow!
Of course, black lights aren’t only used at dance clubs; there are many practical uses as well. Mechanics use them to find tiny leaks by injecting fluorescent dye into the liquid that might be leaking, police use them to check if money is counterfeit since US money has an invisible fluorescent strip in each bill and forensic scientists use the lights at crime scenes to find fingerprints and other evidence.
Whether used to solve a crime or just to make the dance floor glow – black lights can be a fun thing to have around.
C. Hilios writes for ATG Stores. Check out the black light selection at DJ Lighting Effects and Disco Lighting Effects.
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