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What are black lights?


Black lights, also known as UV lights, are lamps that emit electromagnetic radiation. (Scientists refer to them as Wood's Lamp.) Black lights look like regular lights when they are off; when switched on, pure white and fluorescent objects glow in the dark. If you turn on a black light in a dark room, a purpleish glow will emit from the bulb. A black light is similar to a fluorescent lamp, just with some modifications.
There are two different types of black lights. One is a tube black light. This model has a phosphor coating that fluorescent lights do not. This absorbs harmful UV-B and UV-C light. It emits UV-A light because this is the only visible light that can be passed through. There are also incandescent black light bulbs. These are similar to a normal houshold bulb. These bulbs use light filters to absorb light from the heated filament. It absorbs everything but infrared, UV-A light, and a little bit of visible light. This type is not as good at producing black light as a tube black light.
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Tube Black Light and Incandescent Black Light Bulb


What is UV light?


UV light, or Ultraviolet light, comes mostly from the sun; it is the most natural and common source. Ultraviolet light is light with a wavelength shorter than that of visible length, but longer than x-rays. The regular human eye cannot see ultraviolet light because it has limits to what it can see. We can only detect certain waves of light, unlike animals, who can hear and see many things that humans cannot. Human beings cannot detect ultraviolet, infared, gamma or x-rays.There are different types of UV light: UV-A, UV-B, and UV-C. UV-C almost never reaches the earth's surface because it is blocked by the atmosphere. Humans also manufacture these different types of UV light for industrial, commercial, and scientific purposes. UV light is more energetic than other visible light, and has a shorter wavelength, letting it penetrate more readily through objects. UV light was discovered in 1801 by Johan Wilhelm Ritter, the second time light invisible to the naked eye was found. The "ultraviolet" in UV light is a reference to the fact that UV light is beyond violet on the electromagnetic spectrum.
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Fake neon light using plastic tubing and a black light


How do fluorescent lights work?


Fluorescent lights make light by passing electricity through a tube with inert gas and mercury. The mercury atoms emit energy in light photons when energized. When the photon hits a phosphor atoms, an electron from the photon jumps to a higher energy level, making the entire atom vibrate, which creates heat. When the electron falls down to its normal energy level, energy is released in the form of another photon. This photon had less energy than the original, due to some energy that was lost in the heat, but it gives off a visible wite light.


How do black lights work?


Black lights are similar to the fluorescent lights described above. The big difference between a black light and a fluorescent light is the coating and the fact that black lights are made with dark blue glass. The white phosphorus coating on the black lights are meant to absorb the harmful UV rays and only emit somewhat harmless rays. Black lights are more powerful than fluorescent lights because there is a greater amount of light created in the tube. The tube will then emit more UV-A light, thus creating the glow. The UV waves from the black light reacts with the phosphorus coating and the environment, which creates light. Black lights make things glow because of reactions on an atomic level. If the black light were to give off any other type of light, such as infrared or gamma, the bulb wouldn't be fluorescent.

Black Light
Black Light

What are phosphors?


Phosphors are any substance that emit visible light in response to radiation (such as a black light). It converts energy from the black light to visible light. There are many phosphors in our teeth and fingernails, as well as television screens, some types of paint, fabric, plastic, laundry detergent, and high-liters. New white paper, made after 1950, also has phosphorus chemicals in it to seem whiter and brighter. The old paper does not have this, which makes detecting forgeries easier.
Phosphorescence makes the object glow because of the excited state of the atoms, even after the black light is turned off. Phosphorescence lasts longer than regular fluorescence because it takes longer for the atoms to return to their normal orbital state. Fluorescent atoms return to their normal state immediately.

Substances that glow under black lights:
  • White paper
  • Petroleum jelly
  • Teeth and fingernails
  • Body fluids
  • Vitamins
  • Chlorophyll
  • Anti-Freeze
  • Laundry Detergents (and some other cleaners, such as Mr. Clean)
  • Jellyfish
  • Postage Stamps
  • Old Bananas
  • Some types of minerals and gems


How are black lights made and what are they made of?


Black lights contain small amounts of mercury that react with the energy sent through the bulb to create light. Black lights are made with dyed glass to block off most of the visible light given off by the bulb, so that only the ultra-violet rays are emitted. Instead of it having a purplish glow, if a perfect dye were available to us, then there would be a black glow. If black lights were made from clear glass, then the glow would light up the entire room, because the mercury in the bulbs give off blue and green light.
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Black Light Art



What are they used for?


Black lights are commonly thought of as a party light because of the affect it has on textiles and clothing, causing them to glow, especially those white in color. However, black lights can be used for many things, from decoratvie and artistics effects, to diagnostic and therapeutic uses in medicine. Black lights make unusual and dramatic effects. It is often used in the theater to add drama to the performance. Artists use black lights to add emphasis and creativity to their work. Black lights are also used in inspection departments for quality control of manufactured parts and raw materials involved in mass production. Black lights also play an important role in the military. Shannon’s Aqueous Tracers are used in conjunction with black lights to detect leaks of aircraft fuel tanks, circuit board quality control, tool marking and business forms of identification. These invisible tracers are becoming more and more common, and useful in this day and age. The government can detect counterfeit money and counterfeit documents by black light as well. It can be used for certain kinds of security. One of the biggest uses for black lights is at crime scenes, where forensic scientists try to find fingerprints and bodily fluids, such as semen. Repairmen use black lights to detect invisible leaks, especially in air conditioners. Appraisers use black lights to find forgeries in money in antiques. Older paints dont' contain the phosphors that new ones do. Clubs and amusement parks use black lights and phosphor paint as hand stamps for readmission.


Safety Problems

UV lamps such as those used in a laboratory, deliver UV light at a much higher intensity than the sun, and therefore, can cause injury much more quickly to an individual, without their knowledge. Exposure to UV light does not cause pain until several hours after exposure. Skin and eye damage can occur from exposure to the UV light. This damage occurs at wavelengths around 320 nm and shorter. UV lamps, such as black lights, that are sold to the public for general use are almost always filtered to remove the harmful UV wave lengths. Too much exposure to UV rays is not healthy for a person to be exposed to. It can be said that exposure to certain types of black lights is the equivalent to spending one unprotected day in the sun.


What are fluorescent paints?


Fluorescent paints are the brightest paint under a black light. They are often used for posters, Halloween, decorative uses, and in clubs. It is most oftenly used in the entertainment industry. These paints react with the UV light emitted from black lights. They absorb the black light and in return, emit a visible glowing light. Fluorescent paint can eithe
Fluorescent Body Paint
Fluorescent Body Paint
r be visible or invisible. The invisible fluorescent paints will appear white or clear under a regular fluorescent light, but will glow under a black light. Visible fluorescent paint is still visible under a normal light, but will glow brighter under a black light. Something similar is a phosphorescent paint, which is also known as a "glow in the dark" paint. Instead of under a black light, this paint glows in the normal darkness. It will last for minutes, sometimes hours, but will eventually fade without anymore exposure to light.
The making of these paints are similar to how normal paint is made. Paint consists of three basic elements: carriers, pigments, and binders. Fluorescent paint uses ultraviolet pigments, which will make the black light reflect the colors. Binders are used to enable the painter to apply paint to different surfaces, rather than the paint melt off. Carriers define the type of paint being used. They can be in the form of oil (for oil paints), or water (for water colors). In latex paints, a rubbery substance is used.
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Black Light Spin Art


Bibliography



"Electronic Devices: How Black Lights Work." Essortment Articles: Free Online Articles on Health, Science, Education & More.. 2002. Web. 29 May 2010. http://www.essortment.com/hobbies/howblacklights_samu.htm.

Harris, Tom. "HowStuffWorks "Black Light Designs"" Howstuffworks "Science" Discovery, 2002. Web. 28 May 2010. http://science.howstuffworks.com/black-light1.htm.

Helmenstine, Anne Marie. "Materials That Glow Under Black Light." Chemistry - Periodic Table, Chemistry Projects, and Chemistry Homework Help. 2010. Web. 29 May 2010. http://chemistry.about.com/cs/howthingswork/f/blblacklight.htm.

Lee, Ezmeralda. "How Is Fluorescent Paint Made?" How To Do Just About Everything! Web. 30 May 2010. http://www.ehow.com/how-does_4966231_how-fluorescent-paint-made.html. Rudd Cycleback, David.

"Ultraviolet Light and Black Light: a Beginner's Guide." Center for Art and Artifact Studies -- Cycleback.com. Web. 28 May 2010. http://www.cycleback.com/blacklight/five.html.

"What is UV Light?." Wise Geek. N.p., n.d. Web. 4 June 2010. <http://www.wisegeek.com/what-is-uv-light.htm>.

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