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From Wikipedia

Black light

A black light, also referred to as a UV light, is a lamp that emits electromagnetic radiation almost exclusively in the soft near ultraviolet range that is only partially visible. Black light sources may be made from specially designed fluorescent lamps, mercury vapor lamps, light-emitting diodes, or incandescent lamps. Most of these light-emitting devices are placed within a lamp enclosure designed to reduce the emission of visible light and pass desired parts of the ultraviolet spectrum. In medicine, forensics, and some other scientific fields, such a light source is referred to as a Wood's lamp (named for Robert Williams Wood).

The place on the edge of the visible spectrum gives black light its notable characteristics. It is mainly seen by humans using the low-light receptors in the eye, because the low-light receptors are the most sensitive to near ultra-violet. The low-light receptors however also have the distinctive feature that they are more accurate in the peripheral vision, this means black light always will look out of focus when looked at directly.

Black light sources have many uses. They may be employed for decorative and artistic lighting effects, for diagnostic and therapeutic uses in medicine, for the eradication of microorganisms, for the observation or detection of substances tagged with other substances that exhibit a fluorescent effect, for the curing of plastic resins and for attracting insects. Strong sources of long-wave ultraviolet light are used in tanning beds. Black light lamps are used for the detection of counterfeit money. Most artificial ultraviolet sources are low power. Powerful ultraviolet sources present a hazard to eyes and skin; apparatus using these sources requires personal protective equipment.

Types of black lights

Fluorescent

Black light fluorescent tubes are typically made in the same way as normal fluorescent lights except that only one phosphor is used and the normally clear glass envelope of the bulb may be replaced by a deep-bluish-purple glass called Wood's glass. Wood's glass is anickel-oxide–doped glass, which blocks out almost all of the visible light, that is, energy in the electromagnetic spectrum with a wavelength of between about 400 and 700 nanometers. In practice, partly due to cost but mainly because Wood's glass does not make a satisfactory material for lamp manufacturing, the lamp will be made from normal glass with a relatively thin coating of a UV filtering material applied to the exterior. The color of such lamps is often referred to in the trade as "blacklight blue" or "BLB." This is to distinguish these lamps from "bug zapper" blacklight ("BL") lamps that do not have the filter material.

The phosphor typically used for a near 368 to 371 nanometer UV emission peak is either europium-doped strontiumfluoroborate (SrB4O7F:Eu2+) or europium-doped strontium borate (SrB4O7:Eu2+) while the phosphor used to produce a peak at around 350–353 nm is lead-doped bariumsilicate (BaSi2O5:Pb+). "Blacklight Blue" lamps peak at 365 nm.

Manufacturers use different numbering systems for black light, UVA, UVB and Actinic tubes. Philips uses one system which is becoming outdated (2010), while the (German) Osram system is becoming dominant outside North America. The following table lists the tubes generating blue, UVA and UVB, in order of decreasing wavelength of the most intense peak. Approximate phosphor compositions, major manufacturer's type numbers and some uses are given as an overview of the types available. "Peak" position is approximated to the nearest 10 nm. "Width" is the measure between points on the shoulders of the peak that represent 50% intensity.

Wood's glass tubes manufactured by Osram use a fairly narrow-band emitting phosphor, europium activated strontium pyroborate with a peak at about 370 nm, whereas North American and Philips Wood's glass tubes use lead-activated calcium metasilicate that emits a wider band with a shorter wavelength peak at about 350 nm. These two types seem to be the most commonly used. Different manufacturers offer either one or the other and sometimes both.

"Bug zapper" tubes

Some UV fluorescent bulbs are designed for use, particularly in kitchens, to attract insects for electrocution in bug zappers. These use the same near-UV emitting phosphor as normal black lights, but use plain glass instead of the more expensive Wood's glass or filter-coated glass. Plain glass blocks out less of the visible mercury emission spectrum, making them appear light blue-violet to the naked eye. These lamps are referred to as "blacklight" or "BL" in most North American lighting catalogs.

European equivalents are the Philips TL-XXW/09, emitting a peak at 350 nm, and the Osram LXXW/78, emitting a peak at 371 nm, among others.

Incandescent

A black light may also be formed by simply using Wood's glass as the envelope for a common incandescent bulb. This was the method that was used to create the very first black light sources. Although it remains a cheaper alternative to the fluorescent method, it is exceptionally inefficient at producing UV light since most of its electromagnetic energy has to be trapped. Due to its black body spectrum, an incandescent light radiates less than 0.1% of its energy as UV light. Incandescent UV bulbs, due to the necessary absorption of the visible light, become very hot during use. This heat is, in fact, encourage


From Yahoo Answers

Question:i have this giant black light thats like 48 inches. When ever i turn it on it gives off this high pitch frequency sound, it kinda makes me dizzy and if i leave it on too long, a while after i turn it off it continues to make me fee light headed and dizzy. Are there any effects to having a blacklight this big?

Answers:No....it will just irritate you. Why keep it on if it makes you feel funny. Unless its its a fun feeling like nitrous oxide or something along those lines.

Question:I'm thinking about getting a couple black lights for my bedroom to have on every once in a while to see stuff glow but not too often. But some people are saying that it could cause skin cancer and harmful for my eyes and just a bunch of negativity that I really don't wanna here. Well...are they true?

Answers:The honest answer is that if you were around it 24 hours a day for 5 years, it's probaly not that great for you. But using it occasionally is not going to have ill effects. They DO emit UV rays but they are in the frequency which does NOT cause skin cancer. But they can have some ill effects, like I said, if you use it constantly for years and years.

Question:I'm looking for information about the black lights that illuminate florescante stuff. I want to know the different kinds of the lights, the most expensive, and where to buy one. NO STUPID ANSWERS! thanks.

Answers:Hey, Ste, There are a bunch of them. Understand that "Black Light" is essentially Near UV light, so any light that puts out light NEAR the UV spectrum could "kinda/sorta" be called a "Black Light." (It's Kinda / Sorta the way that "Brick Red" is "Kinda / Sorta" like "Red." or how "Aqua" could "Kinda / Sorta" be called "Blue." We're dealing in uncertain terms, here!) The reason I bring this up is that "Black Light" isn't a TYPE of lightbulb. (As you already know.) It's a "color" (and, I use the term loosely.) In the same way that a flourescent blub can have a red lens put in front of it so that it casts a red glow, a "Black Light" blub can be just a regular old light bulb with a deep violet lens. But that's not what you're looking for. You're looking for an Ultra-Violet light. TRUE UV. Not the fake stuff. So, let's start with the fake stuff, so you know what to avoid. First, avoid any UV light that looks like a common light bulb. (Namely, if it's screw-in, and incandescent.) Reason: The "light" made from this bulb actually comes from the glowing of a fillament, which glows at a frequency that emits EVERY color (essentially "White.") What they do is introduce a dye in the glass part of the bulb to reduce the majority of every color OTHER than Violet / Ultraviolet. The end result is that you wind up with a VERY hot bulb which generally doesn't produce much UV light because it's all been converted to heat. All told, you're getting less than .1% (1/1000th) of the light based on how much electricity you're putting in. So, that leaves: - Mercury Vapor (aka: Flourescent) bulbs - LEDs LEDs are probably the most expensive, AND they don't give the best results. (Remember: Even super-bright white LEDs only put out a few watts AT BEST, and cost upwards of $50 for the privilege!) Mercury Vapor (aka: "Flourescent") bulbs will give you the most blacklight output for the least cash. Of course, the PURPOSE of the bulb has to be considered in where to buy one. Looking for big ones (like, to light up a dance club?) Home Depot carries those. Looking for LEDs? Check out http://www.blacklight.com/items/GGL60SUV For more information, check out http://en.wikipedia.org/wiki/Black_light . HEY! ONE MORE THING! BE CAREFUL!!! Excessive Black Light exposure is like being out in the summer sun getting a tan. Tanning can be dangerous because of the UV rays that strike your skin, and can cause skin cancer. Same thing holds true for Black Lights. Be safe! Hope that helps! - Z

Question:Determine the frequency of light with a wavelenth of 4.257 x 10^-7 cm What type of electromagnetic radiation is it? I think i got it.. not sure though... And i know 500nm = green but what is the frequency of this light? (1nm = 1 x 10^-9)

Answers:fw=c f=frequency of light w=wavelenth c= speed of light f=3*10^8/4.257 x 10^-9 =7.0472x10^16 hertz

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