Spectrum of a fluorescent black light source. FWHM spectral bandwidth of the 370nm peak is about 20nm. A full width at half maximum ( FWHM) is an expression of the extent of a function given by the difference between the two extreme values of the Independent variable

Black light (also Wood's light) is the common name for a lamp emitting electromagnetic radiation that is almost exclusively in the soft near ultraviolet range, and very little visible light. A light fixture is an electrical device used to create artificial light or illumination Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays In many areas this type of lighting is more commonly referred to as simply "UV light". The black light was invented by William H. Byler.

Description

Fluorescent black lights are typically made in the same fashion 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, a nickel-oxide–doped glass, which blocks almost all visible light above 400 nanometers. A fluorescent lamp or fluorescent tube is a Gas-discharge lamp that uses Electricity to excite mercury Vapor. A phosphor is a substance that exhibits the phenomenon of Phosphorescence (sustained glowing after exposure to energized particles such as Electrons Wood's glass was developed by Robert Williams Wood (1868&ndash1955 as a light filter used in communications during World War I. Nickel (ˈnɪkəl is a metallic Chemical element with the symbol Ni and Atomic number 28 An oxide is a Chemical compound containing at least one Oxygen atom as well as at least one other element In Semiconductor production doping is the process of intentionally introducing impurities into an extremely pure (also referred to as intrinsic) semiconductor to 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 don't have the blue Wood's glass.

The phosphor typically used for a near 368 to 371 nanometer emission peak is either europium-doped strontium fluoroborate (SrB₄O₇F:Eu²⁺) or europium-doped strontium borate (SrB₄O₇:Eu²⁺) while the phosphor used to produce a peak around 350 to 353 nanometers is lead-doped barium silicate (BaSi₂O₅:Pb⁺). Europium (jʊˈroʊpiəm is a Chemical element with the symbol Eu and Atomic number 63 Strontium (ˈstrɒntiəm /ˈstrɒnʃiəm/) is a Chemical element with the symbol Sr and the Atomic number 38 Borates in Chemistry are Chemical compounds containing Boron bonded to three Oxygen atoms written as B(OR3 Characteristics Lead has a dull luster and is a dense, Ductile, very soft highly Barium (ˈbɛəriəm is a Chemical element. It has the symbol Ba, and Atomic number 56 For the Artificial intelligence Androids of the 1990s Science fiction series Space Above and Beyond, see Silicate (AI "Blacklight Blue" lamps peak at 365 nm.

A black light may also be formed by simply using Wood's glass instead of clear glass as the envelope for a common incandescent bulb. Wood's glass was developed by Robert Williams Wood (1868&ndash1955 as a light filter used in communications during World War I. The incandescent light bulb, incandescent lamp or incandescent light globe is a source of electric Light that works by Incandescence, (a general This was the method used to create the very first black light sources. Though it remains a cheaper alternative to the fluorescent method, it is exceptionally inefficient at producing UV light (a mere few lumens per watt) owing to the black body nature of the incandescent light source. In Physics, a black body is an object that absorbs all light that falls on it Incandescent UV bulbs, due to their inefficiency, may also become dangerously hot during use. More rarely still, high power (hundreds of watts) mercury vapor black lights can be found which use a UV emitting phosphor and an envelope of Wood's glass. These lamps are used mainly for theatrical and concert displays and also become very hot during normal use.

Some UV fluorescent bulbs specifically designed to attract insects for use in bug zappers use the same near-UV emitting phosphor as normal blacklights, but use plain glass instead of the more expensive Wood's glass. A bug zapper is a device that attracts and kills Insects that are attracted by light Plain glass blocks less of the visible mercury emission spectrum, making them appear light blue to the naked eye. These lamps are referred to as "blacklight" or "BL" in most lighting catalogs.

Ultraviolet light can be also generated by some light-emitting diodes.

Safety

While "black lights" do produce light in the UV range, their spectrum is confined to the longwave UVA region. UVA is considered the safest of the three spectra of UV light. It is the higher energy (shortwave) light in the UVB and UVC range that is responsible for the DNA damage that leads to skin cancer. UVA light is much lower in energy and does not cause sunburn. UVA is capable of causing damage to collagen fibers, so it does have the potential to accelerate skin aging and cause wrinkles. UVA can also destroy vitamin A in the skin.

UVA light can cause DNA damage, but not directly like UVB and UVC, it does so indirectly by producing reactive chemical intermediates, such as hydroxyl and oxygen radicals, which in turn can damage DNA. The strength of a black light in comparison to sunlight is minuscule, so it is doubtful that UVA light poses any significant health risks. The weak output of black lights should not cause DNA damage or cellular mutations the way sunlight can.

Uses

Semen under Ultraviolet light (top), and under normal light (bottom).

Fluorescent makeup used for artistic effect.

"Midnight bowling" utilizing blacklights and the fluorescence of pins to enhance ambience. Bowling is a Game / Sport in which players attempt to score points by rolling a Bowling ball along a flat surface either into objects called pins

A scorpion under a blacklight. Scorpions are eight-legged Carnivorous Arthropods They are members of the order Scorpiones within the class Arachnida. In normal lighting this scorpion appears black. Blacklights are often used to find scorpions in the wilderness.

The ultraviolet radiation itself is invisible to the human eye, but illuminating certain materials with UV radiation prompts the visible effects of fluorescence and phosphorescence. Fluorescence is a Luminescence that is mostly found as an Phosphorescence is a specific type of Photoluminescence related to fluorescence. Black light testing is commonly used to authenticate antiques and banknotes. An antique ( Latin: antiquus; old is an old Collectible item It is collected or desirable because of its age rarity condition utility or other unique A banknote (often known as a bill, paper money or simply a note) is a kind of Negotiable instrument, a Promissory note made by a It is extensively used in non-destructive testing; fluorescing fluids are applied to metal structures and illuminated with a black light. The M acro E xpansion T emplate A ttribute L anguage complements TAL, providing macros which allow the reuse of code across Cracks and other artifacts can easily be detected. It is also used to detect pet excreta for elimination, such as urine, vomit and other substances that are not always visible to the naked eye.

It is also used to illuminate pictures painted with fluorescent colors (preferably on black velvet to intensify the illusion of self-illumination). Velvet is a type of tufted fabric in which the cut threads are very evenly distributed with a short dense pile giving it a distinct feel The fluorescence it prompts from certain textile fibers, especially those bearing optical brightener residue, is also used as a recreational effect (as seen for instance in the opening credits of the James Bond film A View to a Kill). Optical brighteners, optical brightening agents (OBAs, fluorescent brightening agents (FBAs or fluorescent whitening agents (FWAs are Dyes James Bond 007 is a Fictional character created in 1953 by writer Ian Fleming, who featured him in twelve Novels and two Short story A View To A Kill (1985 is the fourteenth Spy film of the James Bond series, and the seventh and last to star Roger Moore as the fictional

In forensic investigations, black lights are used to reveal the presence of trace evidence, such as blood, urine, semen and saliva, by causing visible fluorescence in these substances. Trace evidence contends that every contact no matter how slight will leave a trace Blood is a specialized Bodily fluid that delivers necessary substances to the body's cells ��such as nutrients and oxygen—and transports Waste products Urine is a liquid waste product of the body secreted by the Kidneys by a process of filtration from Blood and Excreted through the Urethra. Physiological aspects Internal and external fertilization Depending on the Species, spermatozoa can fertilize For the band see Saliva (band; for the village in Azerbaijan see Səliva. The use of this technique by exposé style television news magazines for reporting on the various unsanitary and mysterious stains found in hotel rooms has become such an oft-repeated stunt that it has been lampooned on comedy shows such as Family Guy and The Office (US). Investigative journalism is a type of reporting in which reporters deeply investigate a topic of interest often involving crime Political corruption, or some other Scandal A newsmagazine, also spelled news magazine, is usually a weekly Magazine featuring articles or segments on current events Family Guy is an animated American television sitcom created by Seth MacFarlane that airs on Fox and regularly on other

In medicine, the Wood's lamp is used to check for the characteristic fluorescence of certain dermatophytic fungi such as Microsporan species which emits a yellow glow, or corynebacterium which have a red to orange color under the Wood's lamp. Corynebacterium is a Genus of Gram-positive,aerobic or facultatively anaerobic, non- Motile, non-sporulated rod-shaped Actinobacteria It is also used to detect the presence and extent of depigmenting disorders such as vitiligo. Vitiligo (ˈvɪtəˈlaɪgoʊ or leukoderma is a chronic skin disease that causes loss of pigment, resulting in irregular pale patches of Skin It can also be used to diagnose ringworm, fungal infections, corneal scratches, foreign bodies in the eye, blocked tear ducts, acne, erythrasma, tinea versicolor, microsporum canis, scabies, alopecia, porphyria, bacterial infections, and many other skin conditions[1][2]. Ringworm (also called serpigo) is an infection of the skin characterized by a reddish to brownish raised or bumpy patch of skin that may be lighter in the center Mycosis (plural mycoses) is a condition in which Fungi pass the resistance barriers of the human or animal body and establish Infections Classification Acne vulgaris (commonly called acne) is a Skin disease caused by changes in the Pilosebaceous units (skin structures consisting of a Hair follicle Erythrasma is a Skin disease that can result in pink patches which can turn into brown scales Tinea versicolor or Pityriasis versicolor is a common skin Infection caused by the Yeast Malassezia furfur (formerly Scabies is a transmissible ectoparasite Skin Infection characterized by superficial Burrows intense pruritus (itching and Secondary Alopecia or hair loss is the medical description of the loss of hair from the head or body sometimes to the extent of Baldness. Porphyrias are a group of inherited or acquired disorders of certain Enzymes in the Heme biosynthetic pathway (also called Porphyrin pathway

In security, a pen with a fluorescent ink, generally a soft tip, is used to "invisibly" mark items. If the items are stolen then a black light can be used to search for the security markings.

Black lights are also used to differentite real banknotes with counterfeit banknotes as, in many countries, real banknotes have fluorescent symbols on them that only show under a black light. A banknote (often known as a bill, paper money or simply a note) is a kind of Negotiable instrument, a Promissory note made by a A counterfeit is an imitation that is made usually with the intent to deceptively represent its content or origins Through this, security officers can check for counterfeit banknotes.

One of the innovations for night and all-weather flying used by the US, UK and Germany during 1939-1945 was the use of UV floodlights to illuminate the instrument panel, giving a variable intensity alternative to the radium painted instrument faces and pointers, without visible illumination that would give away an aircraft's position. Germany, officially the Federal Republic of Germany ( ˈbʊndəsʁepuˌbliːk ˈdɔʏtʃlant is a Country in Central Europe. This went so far as to include the printing of charts that were marked in UV-fluorescent inks, and the provision of UV-visible pencils and slide rules such as the E6B. A pencil is a Writing or Drawing instrument consisting of a thin stick of Pigment (usually Graphite, but can also be coloured pigment or The slide rule, also known as a slipstick, is a mechanical Analog computer. StudentE6BFlightComputerjpg|thumb|An E6B flight computer commonly used by student pilots However, the common failure of the light's power inverter on take-offs in bombers, and the night-blindness and crashes caused when the blacklight filter fell off on trainer aircraft led to the system being mostly abandoned.

Black light puppetry is also performed in a black light theatre. The black light puppet is a form of Puppetry. The Famous People Players of Toronto are internationally renowned in this field

References

See also

• Wood's lamp
• List of light sources

External links

• About.com - "What Materials Glow Under a Black or Ultraviolet Light?"
• - "Medical Uses for a Wood's Lamp"