False-color image of the Sun's corona as seen in deep ultraviolet by the Extreme ultraviolet Imaging Telescope
Black light fluorescent tubes, a common source of long wave (UVA) ultraviolet.

Ultraviolet (UV) light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV. It is named because the spectrum consists of electromagnetic waves with frequencies higher than those that humans identify as the color violet.

Although ultraviolet radiation is invisible to the human eye, most people are aware of the effects of UV through sunburn,and in tanning beds. The UV spectrum has many other effects, both beneficial and damaging, to human health.

UV light is found in sunlight and is emitted by electric arcs and specialized lights such as black lights. It can cause chemical reactions, and causes many substances to glow or fluoresce. Most ultraviolet is classified as non-ionizing radiation. The higher energies of the ultraviolet spectrum from about 150 nm ('vacuum' ultraviolet) are ionizing, but this type of ultraviolet is not very penetrating and is blocked by air.[1]



The discovery of UV radiation was associated with the observation that silver salts darken when exposed to sunlight. In 1801, the German physicist Johann Wilhelm Ritter made the hallmark observation that invisible rays just beyond the violet end of the visible spectrum were especially effective at lightening silver chloride-soaked paper. He called them "oxidizing rays" to emphasize chemical reactivity and to distinguish them from "heat rays" at the other end of the visible spectrum. The simpler term "chemical rays" was adopted shortly thereafter, and it remained popular throughout the 19th century. The terms chemical and heat rays were eventually dropped in favour of ultraviolet and infrared radiation, respectively.[2]

The discovery of the ultraviolet radiation below 200 nm, named vacuum ultraviolet because it is strongly absorbed by air, was made in 1893 by the German physicist Victor Schumann.[3]

Origin of the term

The name means "beyond violet" (from Latin ultra, "beyond"), violet being the color of the shortest wavelengths of visible light. UV light has a shorter wavelength than violet light.


The electromagnetic spectrum of ultraviolet light can be subdivided in a number of ways. The draft ISO standard on determining solar irradiances (ISO-DIS-21348)[4] describes the following ranges:

Name Abbreviation Wavelength range in nanometers Energy per photon
Before UV spectrum Visible light above 400 nm below 3.10 eV
Ultraviolet A, long wave, or black light UVA 400 nm–315 nm 3.10–3.94 eV
Near NUV 400 nm–300 nm 3.10–4.13 eV
Ultraviolet B or medium wave UVB 315 nm–280 nm 3.94–4.43 eV
Middle MUV 300 nm–200 nm 4.13–6.20 eV
Ultraviolet C, short wave, or germicidal UVC 280 nm–100 nm 4.43–12.4 eV
Far FUV 200 nm–122 nm 6.20–10.2 eV
Vacuum VUV 200 nm–100 nm 6.20–12.4 eV
Low LUV 100 nm–88 nm 12.4–14.1 eV
Super SUV 150 nm–10 nm 8.28–124 eV
Extreme EUV 121 nm–10 nm 10.2–124 eV
Beyond UV range X-rays below 10 nm above 124 eV

In photolithography and laser technology, the term deep ultraviolet or DUV refers to wavelengths below 300 nm. Extreme Ultraviolet stands here for discrete spectral ranges of around 13.5 nm (in future planned also 6.x nm) of about 2 % bandwidth. In fields like analytics and life sciences, the acronym "XUV" is used for Extreme Ultraviolet for characterizing the broader spectral range, such as to distinguish from EUV. XUV is separated from x-rays and VUV, by the fact that the photoelectron ionization of innershell electrons is the - by orders of magnitudes - dominating photon-matter interaction effect. This is in contrast to x-rays, where scatter is relevant and VUV where the interaction is mainly with outer ("chemical active") electrons of the atoms and molecules.

"Vacuum UV" is so named because it is absorbed strongly by air and is, therefore, used in a vacuum. In the long-wave limit of this region, roughly 150–200 nm, the principal absorber is the oxygen in air. Work in this region can be performed in an oxygen-free atmosphere, pure nitrogen being commonly used, which avoids the need for a vacuum chamber.

See 1 E-7 m for a list of objects of comparable sizes.

Sources of UV

Natural sources of UV

The sun emits ultraviolet radiation in the UVA, UVB, and UVC bands. The Earth's ozone layer blocks 97-99% of this UV radiation from penetrating through the atmosphere.[5] Of the ultraviolet radiation that reaches the Earth's surface, 98.7% is UVA.[citation needed] (UVC and more energetic radiation is responsible for the generation of the ozone layer, and formation of the ozone there). Extremely hot stars emit proportionally more UV radiation than the sun; the star R136a1 has a thermal energy of 4.57 eV, which falls in the near-UV range.

Ordinary glass is partially transparent to UVA but is opaque to shorter wavelengths, whereas silica or quartz glass, depending on quality, can be transparent even to vacuum UV wavelengths. Ordinary window glass passes about 90% of the light above 350 nm, but blocks over 90% of the light below 300 nm.[6][7][8]

Vacuum UV, which begins at 200 nm, can of course propagate through a vacuum—hence the name—but air is opaque to it, as these wavelengths are strongly absorbed by molecular oxygen in the air. Pure nitrogen (with less than about 10 ppm oxygen) is transparent to wavelengths in the range of about 150–200 nm. This has come to have wide practical significance since semiconductor manufacturing processes have been using wavelengths shorter than 200 nm. By working in oxygen-free gas, the equipment does not have to be built to withstand the pressure differences required to work in a vacuum. Some other scientific instruments which operate in this spectral region, such as circular dichroism spectrometers, are also commonly nitrogen-purged.

Extreme UV is characterized by a transition in the physics of interaction with matter: wavelengths longer than about 30 nm interact mainly with the chemical valence electrons of matter, whereas shorter wavelengths interact mainly with inner-shell electrons and nuclei. The long end of the EUV/XUV spectrum is set by a prominent He+ spectral line at 30.4 nm. XUV is strongly absorbed by most known materials, but it is possible to synthesize multilayer optics that reflect up to about 50% of XUV radiation at normal incidence. This technology, which was pioneered by the NIXT and MSSTA sounding rockets in the 1990s, has been used to make telescopes for solar imaging (current examples are SOHO/EIT and TRACE), and equipment for nanolithography (printing of very small-scale traces and devices on microchips).

"Black lights"

Two black light fluorescent tubes, showing use. The top is a F15T8/BLB 18 inch, 15 watt tube, used in a standard plug-in fluorescent fixture. The bottom is an F8T5/BLB 12 inch, 8 watt tube, used in a portable battery-powered black light sold as a pet urine detector.

A black light, Wood's light, or UV light is a lamp that emits long-wave UV radiation and very little visible light. Fluorescent black lights are typically made in the same fashion as normal fluorescent lights, except that a different phosphor is used on the inside of the tube which emits UV instead of visible light, and the 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 nanometres. The color of such lamps is often referred to in the lighting industry as "blacklight blue" or "BLB", to distinguish them from UV lamps used in "bug zapper" insect traps, that do not have the blue Wood's glass. These are designated "blacklight" ("BL") lamps. The phosphor typically used for a near 368 to 371 nanometre 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 nanometres is lead-doped barium silicate (BaSi2O5:Pb+). "Blacklight Blue" lamps peak at 365 nm.

While "black lights" do produce light in the UV range, their spectrum is confined to the long-wave UVA region. Unlike UVB and UVC, which are responsible for the direct DNA damage that leads to skin cancer, black light is limited to lower-energy, longer waves and does not cause sunburn, although it can damage collagen fibers and destroy vitamins A and D in skin.[citation needed]

A black light may also be formed, very inefficiently, by simply using Wood's glass instead of clear glass as the envelope for a common incandescent bulb. This was the method used to create the very first black light sources. Though cheaper than the fluorescent source, only 0.1% of the input power is converted to usable radiation, as the incandescent light radiates as a black body with very little emission in the UV. Incandescent bulbs used to generate significant UV, due to their inefficiency, may become dangerously hot. More rarely still, high-power (hundreds of watts) mercury-vapor black lights that use a UV-emitting phosphor and an envelope of Wood's glass are made, are used mainly for theatrical and concert displays. They also become very hot during normal use.

Some UV fluorescent bulbs specifically designed to attract insects use the same near-UV emitting phosphor as normal blacklights, but use plain glass instead of the more expensive Wood's glass. 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 fluorescent lamps

Fluorescent lamps without a phosphorescent coating to convert UV to visible light, emit ultraviolet light with two peaks at 253.7 nm and 185 nm due to the peak emission of the mercury within the bulb. Eighty-five to ninety percent of the UV produced by these lamps is at 253.7 nm, while only five to ten percent is at 185 nm. Germicidal lamps use quartz (glass) doped with an additive to block the 185 nm wavelength. With the addition of a suitable phosphor (phosphorescent coating) , they can be modified to produce a UVA, UVB, or visible light spectrum (all fluorescent tubes used for domestic and commercial lighting are mercury (Hg) UV emission bulbs at heart).

Such low-pressure mercury lamps are used extensively for disinfection, and in standard form have an optimum operating temperature of about 30 degrees Celsius. Use of a mercury amalgam allows operating temperature to rise to 100 degrees Celsius, and UVC emission to about double or triple per unit of light-arc length. These low-pressure lamps have a typical efficiency of approximately thirty to thirty-five percent, meaning that for every 100 watts of electricity consumed by the lamp, it will produce approximately 30-35 watts of total UV output. UVA/UVB emitting bulbs also sold for other special purposes, such as reptile-keeping.

Ultraviolet LEDs

Light-emitting diodes (LEDs) can be manufactured to emit light in the ultraviolet range, although practical LED arrays are very limited below 365 nm. LED efficiency at 365 nm is about 5-8%, whereas efficiency at 395 nm is closer to 20%, and power outputs at these longer UV wavelengths are also better. Such LED arrays are beginning to be used for UV curing applications, and are already successful in digital print applications and inert UV curing environments. Power densities approaching 3,000 mW/cm2 (30 kW/m2) are now possible, and this, coupled with recent developments by photoinitiator and resin formulators, makes the expansion of LED-cured UV materials likely.

Ultraviolet lasers

UV laser diodes and UV solid-state lasers can be manufactured to emit light in the ultraviolet range. Wavelengths available include 262, 266, 349, 351, 355, and 375 nm. Ultraviolet lasers have applications in industry (laser engraving), medicine (dermatology and keratectomy), secure communications, and computing (optical storage). They can be made by applying frequency conversion to lower-frequency lasers, or from Ce:LiSAF crystals (cerium doped with lithium strontium aluminum fluoride), a process developed in the 1990s at Lawrence Livermore National Laboratory.[9]

Gas-discharge lamps

Argon and deuterium lamps are often used as stable sources, either windowless or with various windows such as magnesium fluoride.[10]

Detecting and measuring UV radiation

Ultraviolet detection and measurement technology can vary with the part of the spectrum under consideration. While some silicon detectors are used across the spectrum, and in fact the US NIST has characterized simple silicon diodes[11] that work with visible light too, many specializations are possible for different applications. Many approaches seek to adapt visible light-sensing technologies, but these can suffer from unwanted response to visible light and various instabilities. A variety of solid-state and vacuum devices have been explored for use in different parts of the UV spectrum. Ultraviolet light can be detected by suitable photodiodes and photocathodes, which can be tailored to be sensitive to different parts of the UV spectrum. Sensitive ultraviolet photomultipliers are available.

Near UV

Between 200-400 nm, a variety of detector options exist.

Vacuum UV

Technology for VUV instrumentation has been largely driven by solar physics for many decades and more recently some photolithography applications for semiconductors. While optics can be used to remove unwanted visible light that contaminates the VUV, in general, detectors can be limited by their response to non-VUV radiation, and the development of "solar-blind" devices has been an important area of research. Wide-gap solid-state devices or vacuum devices with high-cutoff photocathodes can be attractive compared to silicon diodes. Recently, a diamond-based device flew on the LYRA (see also Marchywka Effect).

Human health-related effects of UV radiation

The health effects ultraviolet radiation has on human health has implications on weighting the risks and benefits of sun exposure, but is also implicated in issues such as fluorescent lamps and health.

Beneficial effects

Vitamin D

UVB exposure induces the production of vitamin D in the skin at a rate of up to 1,000 IUs per minute. The majority of positive health effects are related to this vitamin. It has regulatory roles in calcium metabolism (which is vital for normal functioning of the nervous system, as well as for bone growth and maintenance of bone density), immunity, cell proliferation, insulin secretion, and blood pressure.[12]


Too little UVB radiation may lead to a lack of vitamin D. Too much UVB radiation may lead to direct DNA damage, sunburn, and skin cancer. An appropriate amount of UVB (which varies according to skin color) leads to a limited amount of direct DNA damage. This is recognized and repaired by the body, then melanin production is increased, which leads to a long-lasting tan. This tan occurs with a 2-day lag phase after irradiation.

Medical applications

Ultraviolet radiation has other medical applications, in the treatment of skin conditions such as psoriasis and vitiligo. UVA radiation has been much used in conjunction with psoralens (PUVA treatment) for psoriasis, although this treatment is less used now because the combination produces dramatic increases in skin cancer, and because treatment with UVB radiation by itself is more effective. In cases of psoriasis and vitiligo, UV light with wavelength of 311 nm is most effective.[13][14]

Harmful effects

An overexposure to UVB radiation can cause sunburn and some forms of skin cancer. However the most deadly form - malignant melanoma - is mostly caused by the indirect DNA damage (free radicals and oxidative stress). This can be seen from the absence of a UV-signature mutation in 92% of all melanoma.[15] In humans, prolonged exposure to solar UV radiation may result in acute and chronic health effects on the skin, eye, and immune system.[16] Moreover, UVC can cause adverse affects that can variously be mutagenic or carcinogenic.[17]

UVC rays are the highest energy, most dangerous type of ultraviolet light. Little attention has been given to UVC rays in the past since they are filtered out by the atmosphere. However, their use in equipment such as pond sterilization units may pose an exposure risk, if the lamp is switched on outside of its enclosed pond sterilization unit.

On April 13, 2011 the International Agency for Research on Cancer of the World Health Organization classified all categories and wavelengths of Ultraviolet Radiation as a Group 1 carcinogen. This is the highest level designation for carcinogens and means "There is enough evidence to conclude that it can cause cancer in humans".

Ultraviolet photons harm the DNA molecules of living organisms in different ways. In one common damage event, adjacent thymine bases bond with each other, instead of across the "ladder". This "thymine dimer" makes a bulge, and the distorted DNA molecule does not function properly.


Cancer risk
Ultraviolet (UV) irradiation present in sunlight is an environmental human carcinogen. The toxic effects of UV from natural sunlight and therapeutic artificial lamps are a major concern for human health. The major acute effects of UV irradiation on normal human skin comprise sunburn inflammation erythema, tanning, and local or systemic immunosuppression.
— Matsumura and Ananthaswamy , (2004)[18]

UVA, UVB, and UVC can all damage collagen fibers and, therefore, accelerate aging of the skin. Both UVA and UVB destroy vitamin A in skin, which may cause further damage.[19] In the past, UVA was considered less harmful, but today it is known it can contribute to skin cancer via indirect DNA damage (free radicals and reactive oxygen species). It penetrates deeply, but it does not cause sunburn. UVA does not damage DNA directly like UVB and UVC, but it can generate highly reactive chemical intermediates, such as hydroxyl and oxygen radicals, which in turn can damage DNA.[citation needed] Because it does not cause reddening of the skin (erythema), it cannot be measured in SPF testing.[citation needed] There is no good clinical measurement for blockage of UVA radiation, but it is important for sunscreen to block both UVA and UVB. Some scientists blame the absence of UVA filters in sunscreens for the higher melanoma risk found for sunscreen users.[20]

The reddening of the skin due to the action of sunlight depends both on the amount of sunlight and on the sensitivity of the skin ("erythemal action spectrum") over the UV spectrum.

UVB light can cause direct DNA damage. The radiation excites DNA molecules in skin cells, causing aberrant covalent bonds to form between adjacent cytosine bases, producing a dimer. When DNA polymerase comes along to replicate this strand of DNA, it reads the dimer as "AA" and not the original "CC". This causes the DNA replication mechanism to add a "TT" on the growing strand. This mutation can result in cancerous growths, and is known as a "classical C-T mutation". The mutations caused by the direct DNA damage carry a UV signature mutation that is commonly seen in skin cancers. The mutagenicity of UV radiation can be easily observed in bacterial cultures. This cancer connection is one reason for concern about ozone depletion and the ozone hole. UVB causes some damage to collagen, but at a very much slower rate than UVA.[citation needed]

As a defense against UV radiation, the amount of the brown pigment melanin in the skin increases when exposed to moderate (depending on skin type) levels of radiation; this is commonly known as a sun tan. The purpose of melanin is to absorb UV radiation and dissipate the energy as harmless heat, blocking the UV from damaging skin tissue. UVA gives a quick tan that lasts for days by oxidizing melanin that was already present, and triggers the release of the melanin from melanocytes. UVB yields a tan that takes roughly 2 days to develop because it stimulates the body to produce more melanin.[citation needed] The photochemical properties of melanin make it an excellent photoprotectant. Older and more widespread sunscreen chemicals cannot dissipate the energy of the excited state as efficiently as melanin, and, therefore, the penetration of these sunscreen ingredients into the lower layers of the skin may increase the amount of free radicals and reactive oxygen species (ROS).[21] In recent years, improved filtering substances have come into use in commercial sunscreen lotions that do not significantly degrade or lose their capacity to protect the skin as the exposure time increases (photostable substances).[22]

Sunscreen prevents the direct DNA damage that causes sunburn by blockage of UVB.[clarification needed] As such, most of these products contain an SPF rating that indicates how well they block UVB as a measure of their effectiveness. This rating, however, offers no data about protection against UVA, exposure to which does not lead to sunburn but is still harmful.[citation needed] In the US, the Food and Drug Administration is considering adding a star rating system to show UVA protection. A similar system is already used in some European countries.[citation needed] Some sunscreen lotions now include compounds such as titanium dioxide, which helps protect against UVA rays. Other UVA blocking compounds found in sunscreen include zinc oxide and avobenzone.

Sunscreen safety debate
Image of a man's face with sunscreen on the left , in visible (left) and UV light, demonstrating how sunscreen protects against UV exposure. The side of the face with sunscreen, is darker, showing that the sunscreen absorbs the UV light.

Medical organizations recommend patients protect themselves from UV radiation by using sunscreen. Five sunscreen ingredients have been shown to protect mice against skin tumors (see sunscreen).

However, some sunscreen chemicals produce potentially harmful substances if they are illuminated while in contact with living cells.[23][24][25] The amount of sunscreen that penetrates through the stratum corneum may or may not be large enough to cause damage. In one study of sunscreens, the authors write:[26]

The question whether UV filters acts on or in the skin has so far not been fully answered. Despite the fact that an answer would be a key to improve formulations of sun protection products, many publications carefully avoid addressing this question.

In an experiment by Hanson et al. published in 2006, the amount of harmful reactive oxygen species (ROS) was measured in untreated and in sunscreen treated skin. In the first 20 minutes, the film of sunscreen had a protective effect and the amount of ROS was smaller. After 60 minutes, however, the amount of absorbed sunscreen was so high, the amount of ROS was higher in the sunscreen treated skin than in the untreated skin.[21]

Such effects can be avoided by using newer generations of filter substances or combinations that maintain their UV protective properties even after several hours of solar exposure. Sunscreen products containing photostable filters like drometrizole trisiloxane, bisoctrizole, or bemotrizinol have been available for many years throughout the world, but are not yet available in the U.S., whereas another high-quality filter, ecamsule, has also been available in the U.S. since 2006.[22]

Aggravation of skin diseases

Ultraviolet radiation causes aggravation of several skin conditions and diseases, including:


High intensities of UVB light are hazardous to the eyes, and exposure can cause welder's flash (photokeratitis or arc eye) and may lead to cataracts, pterygium,[28][29] and pinguecula formation.

UV light is absorbed by molecules known as chromophores, which are present in the eye cells and tissues. Chromophores absorb light energy from the various wavelengths at different rates - a pattern known as absorption spectrum. If too much UV light is absorbed, eye structures such as the cornea, the lens and the retina can be damaged.

Protective eyewear is beneficial to those who are working with or those who might be exposed to ultraviolet radiation, particularly short wave UV. Given that light may reach the eye from the sides, full coverage eye protection is usually warranted if there is an increased risk of exposure, as in high altitude mountaineering. Mountaineers are exposed to higher than ordinary levels of UV radiation, both because there is less atmospheric filtering and because of reflection from snow and ice.

Ordinary, untreated eyeglasses give some protection. Most plastic lenses give more protection than glass lenses, because, as noted above, glass is transparent to UVA and the common acrylic plastic used for lenses is less so. Some plastic lens materials, such as polycarbonate, inherently block most UV. There are protective treatments available for eyeglass lenses that need it, which will give better protection. But even a treatment that completely blocks UV will not protect the eye from light that arrives around the lens.

Degradation of polymers, pigments and dyes

UV damaged polypropylene rope (left) and new rope (right)

Many polymers used in consumer products are degraded by UV light, and need addition of UV absorbers to inhibit attack, especially if the products are exposed to sunlight. The problem appears as discoloration or fading, cracking, and, sometimes, total product disintegration if cracking has proceeded sufficiently. The rate of attack increases with exposure time and sunlight intensity.

It is known as UV degradation, and is one form of polymer degradation. Sensitive polymers include thermoplastics, such as polypropylene, polyethylene, and poly(methyl methacrylate) as well as speciality fibers like aramids. UV absorption leads to chain degradation and loss of strength at sensitive points in the chain structure. They include tertiary carbon atoms, which in polypropylene occur in every repeat unit. Aramid rope must be shielded with a sheath of thermoplastic if it is to retain its strength.The impact of UV on polymers is used in nanotechnology, transplantology, X-ray lithography and other fields for modification of properties (roughness, hydrophobicity) of polymer surfaces. For example, a poly(methyl methacrylate) surface can be smoothed by vacuum ultraviolet (VUV).[30]

IR spectrum showing carbonyl absorption due to UV degradation of polyethylene

In addition, many pigments and dyes absorb UV and change colour, so paintings and textiles may need extra protection both from sunlight and fluorescent bulbs, two common sources of UV radiation. Old and antique paintings such as watercolour paintings, for example, usually must be placed away from direct sunlight. Common window glass provides some protection by absorbing some of the harmful UV, but valuable artifacts need extra shielding. Many museums place black curtains over watercolour paintings and ancient textiles, for example. Since watercolours can have very low pigment levels, they need extra protection from UV light. Tinted glasses, such as sunglasses also provide protection from UV rays.

Blockers and absorbers

Ultraviolet Light Absorbers (UVAs) are molecules used in organic materials (polymers, paints, etc.) to absorb UV light to reduce the UV degradation (photo-oxidation) of a material. A number of different UVAs with different absorption properties exist. UVAs can disappear over time, so monitoring of UVA levels in weathered materials is necessary.

In sunscreen, ingredients that absorb UVA/UVB rays, such as avobenzone and octyl methoxycinnamate, are known as absorbers. They are contrasted with physical "blockers" of UV radiation such as titanium dioxide and zinc oxide. (See sunscreen for a more complete list.)

Applications of UV

By wavelength:[31]


A bird appears on many Visa credit cards when held under a UV light source

To help prevent counterfeiters, sensitive documents (e.g., credit cards, driver's licenses, passports) may also include a UV watermark that is visible only under a UV-emitting light. Passports issued by most countries usually contain UV sensitive inks and security threads. Visa stamps and stickers on passports of visitors contain large detailed seals invisible under normal light, but strongly visible under UV illumination. Passports issued by many nations have UV sensitive watermarks on all pages. Currencies of various countries' banknotes have an image, as well as many multicolored fibers, that are visible only under ultraviolet light.

Some brands of pepper spray will leave an invisible chemical (UV dye) that is not easily washed off on a pepper sprayed attacker, which would help police identify them later.[33]


UV is an investigative tool at the crime scene helpful in locating and identifying bodily fluids (semen, blood,[citation needed] bile etc.). E.g., ejaculated fluids or saliva are detected by high-power UV, irrespective of the structure or colour of the surface the fluid is deposited upon.[34]

Fluorescent lamps

Fluorescent lamps produce UV radiation by ionising low-pressure mercury vapour. A phosphorescent coating on the inside of the tubes absorbs the UV and converts it to visible light.

The main mercury emission wavelength is in the UVC range. Unshielded exposure of the skin or eyes to mercury arc lamps that do not have a conversion phosphor is quite dangerous.

The light from a mercury lamp is predominantly at discrete wavelengths. Other practical UV sources with more continuous emission spectra include xenon arc lamps (commonly used as sunlight simulators), deuterium arc lamps, mercury-xenon arc lamps, metal-halide arc lamps, and tungsten-halogen incandescent lamps.


Aurora at Jupiter's north pole as seen in ultraviolet light by the Hubble Space Telescope.

In astronomy, very hot objects preferentially emit UV radiation (see Wien's law). Because the ozone layer blocks many UV frequencies from reaching telescopes on the surface of the Earth, most UV observations are made from space. (See UV astronomy, space observatory.)

Biological surveys and pest control

Some animals, including birds, reptiles, and insects such as bees, can see near-ultraviolet light. Many fruits, flowers, and seeds stand out more strongly from the background in ultraviolet wavelengths as compared to human color vision. Scorpions glow or take on a yellow to green color under UV illumination, thus assisting in the control of these arachnids. Many birds have patterns in their plumage that are invisible at usual wavelengths but observable in ultraviolet, and the urine and other secretions of some animals, including dogs, cats, and human beings, is much easier to spot with ultraviolet. Urine trails of rodents can be detected by pest control technicians for proper treatment of infested dwellings.

Butterflies use ultraviolet as a communication system for sex recognition and mating behavior.

Many insects use the ultraviolet wavelength emissions from celestial objects as references for flight navigation. A local ultraviolet emissor will normally disrupt the navigation process and will eventually attract the flying insect.

Entomologist using a UV light for collecting beetles in the Paraguayan Chaco.

Ultraviolet traps called bug zappers are used to eliminate various small flying insects. They are attracted to the UV light, and are killed using an electric shock, or trapped once they come into contact with the device. Different designs of ultraviolet light traps are also used by entomologists for collecting nocturnal insects during faunistic survey studies.


UV/VIS spectroscopy is widely used as a technique in chemistry, to analyze chemical structure, the most notable one being conjugated systems. UV radiation is often used in visible spectrophotometry to determine the fluorescence of a given sample. In biological research, UV light is used for quantification of nucleic acids or proteins.

Sanitary compliance

UV lamps including newer LEDs (light-emitting diode) aid in the detection of organic mineral deposits that remain on surfaces where periodic cleaning and sanitizing may not be properly accomplished. Both urine and phosphate soaps are easily detected using UV inspection. Pet urine deposits in carpeting or other hard surfaces can be detected for accurate treatment and removal of mineral tracers and the odor-causing bacteria that feed on proteins within. Many hospitality industries use UV lamps to inspect for unsanitary bedding to determine lifecycle for mattress restoration as well as general performance of the cleaning staff. A perennial news feature for many television news organizations involves an investigative reporter's using a similar device to reveal unsanitary conditions in hotels, public toilets, hand rails, and such.

Air purification

Using a catalytic reaction from titanium dioxide and UV light exposure, a strong oxidative effect occurs on any organic objects that pass through the media, converting otherwise irritating pathogens, pollens, and mold spores into harmless inert byproducts. The cleansing mechanism of UV is a photochemical process. The contaminants that pollute the indoor environment are almost entirely based upon organic or carbon-based compounds. These compounds break down when exposed to high-intensity UV at 240 to 280 nm. Short-wave ultraviolet light can destroy DNA in living microorganisms and break down organic material found in indoor air. UVC's effectiveness is directly related to intensity and exposure time.

UV light has also been shown (by KJ Scott et al) as effective in reducing gaseous contaminants such as carbon monoxide and VOCs.[35][36][37] Scott and his colleagues demonstrated that the correct mixture of UV lamps radiating at 184 and 254 nm can remove low concentrations of hydrocarbons and carbon monoxide, if the lamps are held in a radiation chamber (a box or drum) and the air is recycled between the room and the reaction chamber. This arrangement prevents the introduction of ozone into the treated air. Alternatively, air may be treated by passing by a single UV source operating at 184 nm and subsequent catalysis with iron pentaoxide. The iron oxides remove the ozone produced by the UV lamp.

Analyzing minerals

A collection of mineral samples brilliantly fluorescing at various wavelengths as seen while being irradiated by UV light.

Ultraviolet lamps are also used in analyzing minerals and gems, and in other detective work including authentication of various collectibles. Materials may look the same under visible light, but fluoresce to different degrees under ultraviolet light, or may fluoresce differently under short wave ultraviolet versus long wave ultraviolet.


In other detective work including authentication of various collectibles and art, and detecting counterfeit currency absent of marker dyes. Materials may look the same under visible light, but fluoresce to different degrees under ultraviolet light, or may fluoresce differently under short-wave ultraviolet versus long-wave ultraviolet.

Chemical markers

UV fluorescent dyes are used in many applications (for example, biochemistry and forensics). The Green Fluorescent Protein (GFP) is often used in genetics as a marker. Many substances, such as proteins, have significant light absorption bands in the ultraviolet that are of use and interest in biochemistry and related fields. UV-capable spectrophotometers are common in such laboratories.


Exposure to UVA light while the skin is hyper-photosensitive by taking psoralens is an effective treatment for psoriasis called PUVA. Due to the potential of psoralens to cause damage to the liver, PUVA may be used only a limited number of times over a patient's lifetime.


Exposure to UVB light, in particular, the 310 nm narrowband UVB range, is an effective long-term treatment for many skin conditions like psoriasis, vitiligo, eczema, and others.[38] UVB phototherapy does not require additional medications or topical preparations for the therapeutic benefit; only the light exposure is needed. However, phototherapy can be effective when used in conjunction with certain topical treatments such as anthralin, coal tar, and Vitamin A and D derivatives, or systemic treatments such as methotrexate and soriatane.[39]

Typical treatment regimes involve short exposure to UVB rays 3 to 5 times a week at a hospital or clinic, and repeated sessions may be required before results are noticeable. Almost all of the conditions that respond to UVB light are chronic problems, so continuous treatment is required to keep those problems in check. Home UVB systems are common solutions for those whose conditions respond to treatment. Home systems permit patients to treat themselves every other day (the ideal treatment regimen for most) without the frequent, costly trips to the office/clinic and back.

Side-effects may include itching and redness of the skin due to UVB exposure, and possibly sunburn, if patients do not minimize exposure to natural UV rays during treatment days. Cataracts can frequently develop if the eyes are not protected from UVB light exposure. There is no link between an increase in the patient's risk for skin cancer and the proper use of UVB phototherapy.[40] "Proper use" is generally defined as reaching the "Sub-Erythemic Dose" (S.E.D.), the maximum amount of UVB your skin can receive without burning.

Certain fungal growths under the toenail can be treated using a specific wavelength of UV delivered from a high-power LED (light-emitting diode) and can be safer than traditional systemic drugs.


Ultraviolet radiation is used for very fine resolution photolithography, a procedure wherein a chemical called a photoresist is exposed to UV radiation that has passed through a mask. The light causes chemical reactions to occur in the photoresist, and, after development (a step that removes either the exposed or the unexposed photoresist), a pattern determined by the mask remains on the sample. Steps may then be taken to "etch" away areas of the sample where no photoresist remains.

UV radiation is used extensively in the electronics industry because photolithography is used in the manufacture of semiconductors, integrated circuit components,[41] and printed circuit boards.

Checking electrical insulation

An application of UV is to detect corona discharge (often called "corona") on electrical apparatus. Degradation of insulation in electrical apparatus or pollution causes corona, wherein a strong electric field ionizes the air and excites nitrogen molecules, causing the emission of ultraviolet radiation. The corona degrades the insulation level of the apparatus. Corona produces ozone and to a lesser extent nitrogen oxide, which may subsequently react with water in the air to form nitrous acid and nitric acid vapour in the surrounding air.[42]


A low pressure mercury vapor discharge tube floods the inside of a hood with shortwave UV light when not in use, sterilizing microbiological contaminants from irradiated surfaces.

Ultraviolet lamps are used to sterilize workspaces and tools used in biology laboratories and medical facilities. Commercially available low-pressure mercury-vapor lamps emit about 86% of their light at 254 nanometers (nm), which coincides very well with one of the two peaks of the germicidal effectiveness curve (i.e., effectiveness for UV absorption by DNA). One of these peaks is at about 265 nm and the other is at about 185 nm. Although 185 nm is better absorbed by DNA, the quartz glass used in commercially available lamps, as well as environmental media such as water, are more opaque to 185 nm than 254 nm (C. von Sonntag et al., 1992). UV light at these germicidal wavelengths causes adjacent thymine molecules on DNA to dimerize; if enough of these defects accumulate on a microorganism's DNA, its replication is inhibited, thereby rendering it harmless (even though the organism may not be killed outright). However, since microorganisms can be shielded from ultraviolet light in small cracks and other shaded areas, these lamps are used only as a supplement to other sterilization techniques.

Disinfecting drinking water

UV radiation can be an effective viricide and bactericide. Disinfection using UV radiation is commonly used in wastewater treatment applications and is finding an increased usage in drinking water treatment. Many bottlers of spring water use UV disinfection equipment to sterilize their water. Solar water disinfection is the process of using PET bottles and sunlight to disinfect water.

New York City has approved the construction of a 2.2 billion US gallon per day (535,000 m3/hr) ultraviolet drinking water disinfection facility due to be online in 2012.[43] There are also several facilities under construction and several in operation that treat waste water with several stages of filters, hydrogen peroxide, and UV light to bring the water up to drinking standards. One such facility exists in Orange County, California which is designed to treat wastewater and convert it into high-quality water for Indirect Potable Reuse.[44][45] NASA has examined the use of this technology, using titanium dioxide as catalyst, for breaking down harmful products in spacecraft waste water.[46]

It used to be thought that UV disinfection was more effective for bacteria and viruses, which have more exposed genetic material, than for larger pathogens that have outer coatings or that form cyst states (e.g., Giardia) that shield their DNA from the UV light. However, it was recently discovered that ultraviolet radiation can be somewhat effective for treating the microorganism Cryptosporidium. The findings resulted in the use of UV radiation as a viable method to treat drinking water. Giardia in turn has been shown to be very susceptible to UV-C when the tests were based on infectivity rather than excystation.[47] It has been found that protists are able to survive high UV-C doses but are sterilized at low doses.

Solar water disinfection[48] (SODIS) has been extensively researched in Switzerland and has proven ideal to treat small quantities of water cheaply using natural sunlight. Contaminated water is poured into transparent plastic bottles and exposed to full sunlight for six hours. The sunlight treats the contaminated water through two synergetic mechanisms: UV-A irradiation and increased water temperature. If the water temperatures rises above 50 °C (120 °F), the disinfection process is three times faster.

Food processing

As consumer demand for fresh and "fresh-like" food products increases, the demand for nonthermal methods of food processing is likewise on the rise. In addition, public awareness regarding the dangers of food poisoning is also raising demand for improved food processing methods. Ultraviolet radiation is used in several food processes to kill unwanted microorganisms. UV light can be used to pasteurize fruit juices by flowing the juice over a high-intensity ultraviolet light source.[49] The effectiveness of such a process depends on the UV absorbance of the juice (see Beer's law).

Fire detection

Ultraviolet detectors generally use either a solid-state device, such as one based on silicon carbide or aluminium nitride, or a gas-filled tube as the sensing element. UV detectors that are sensitive to UV light in any part of the spectrum respond to irradiation by sunlight and artificial light. A burning hydrogen flame, for instance, radiates strongly in the 185- to 260-nanometer range and only very weakly in the IR region, whereas a coal fire emits very weakly in the UV band yet very strongly at IR wavelengths; thus, a fire detector that operates using both UV and IR detectors is more reliable than one with a UV detector alone. Virtually all fires emit some radiation in the UVC band, whereas the Sun's radiation at this band is absorbed by the Earth's atmosphere. The result is that the UV detector is "solar blind", meaning it will not cause an alarm in response to radiation from the Sun, so it can easily be used both indoors and outdoors.

UV detectors are sensitive to most fires, including hydrocarbons, metals, sulfur, hydrogen, hydrazine, and ammonia. Arc welding, electrical arcs, lightning, X-rays used in nondestructive metal testing equipment (though this is highly unlikely), and radioactive materials can produce levels that will activate a UV detection system. The presence of UV-absorbing gases and vapors will attenuate the UV radiation from a fire, adversely affecting the ability of the detector to detect flames. Likewise, the presence of an oil mist in the air or an oil film on the detector window will have the same effect.


Reptiles need long wave UV light for de novo synthesis of vitamin D. Vitamin D is needed to metabolize calcium for bone and egg production. Thus, in a typical reptile enclosure, a fluorescent UV lamp should be available for vitamin D synthesis. This should be combined with the provision of heat for basking, either in the same or by another lamp.

Curing of electronic potting resins

Electronic components that require clear transparency for light to exit or enter (photo voltaic panels and sensors) can be potted using acrylic resins that are cured using UV light energy. The advantages are low VOC emissions and rapid curing.

Curing of inks, adhesives, varnishes and coatings

Certain inks, coatings, and adhesives are formulated with photoinitiators and resins. When exposed to the correct energy and irradiance in the required band of UV light, polymerization occurs, and so the adhesives harden or cure. Usually, this reaction is very quick, a matter of a few seconds. Applications include glass and plastic bonding, optical fiber coatings, the coating of flooring, UV Coating and paper finishes in offset printing, and dental fillings. Curing of decorative finger nail "gels".

An industry has developed around the manufacture of UV sources for UV curing applications. This includes UV lamps, UV LEDs, and Excimer Flash lamps. Fast processes such as flexo or offset printing require high-intensity light focused via reflectors onto a moving substrate and medium; and high-pressure Hg (mercury) or Fe (iron, doped)-based bulbs are used, which can be energized with electric arc or microwaves. Lower-power sources (fluorescent lamps, LED) can be used for static applications, and, in some cases, small high-pressure lamps can have light focused and transmitted to the work area via liquid-filled or fiber-optic light guides.

Sun tanning

Sun tanning describes a darkening of the skin in a natural physiological response stimulated by exposure to ultraviolet radiation from sunshine (or a sunbed). With excess exposure to the sun, a suntanned area can also develop sunburn. The increased production of melanin is triggered by the direct DNA damage.[50] This kind of damage is recognized by the body and as a defense against UV radiation the skin produces more melanin. Melanin dissipates the UV energy as harmless heat, and therefore it is an excellent photoprotectant. Melanin protects against the direct DNA damage and against the indirect DNA damage. Sunscreen protects only against the direct DNA damage, but increases the indirect DNA damage.[23][24][25] Some studies suggest that this may be the cause of the higher incidence of melanoma found in sunscreen users compared to non-users.[51][52][20][53][54]

Erasing EPROM modules

Some EPROM (erasable programmable read-only memory) modules are erased by exposure to UV radiation. These modules often have a transparent glass (quartz) window on the top of the chip that allows the UV radiation in. These have been largely superseded by EEPROM and flash memory chips in most devices.

Preparing low surface energy polymers

UV radiation is useful in preparing low surface energy polymers for adhesives. Polymers exposed to UV light will oxidize, thus raising the surface energy of the polymer. Once the surface energy of the polymer has been raised, the bond between the adhesive and the polymer is stronger.

Reading otherwise illegible papyruses and manuscripts

Using multi-spectral imaging it is possible to read illegible papyruses, such as the burned papyruses of the Villa of the Papyri or of Oxyrhynchus, or the Archimedes palimpsest. The technique involves taking pictures of the illegible papyruses using different filters in the infrared or ultraviolet range, finely tuned to capture certain wavelengths of light. Thus, the optimum spectral portion can be found for distinguishing ink from paper on the papyrus surface. Simple NUV sources can be used to highlight faded iron-based ink on vellum.[55]


Ultraviolet lasers have applications in industry (laser engraving), medicine (dermatology and keratectomy), free air secure communications and computing (optical storage). They can be made by applying frequency conversion to lower-frequency lasers, or from Ce:LiSAF crystals (cerium doped with lithium strontium aluminum fluoride), a process developed in the 1990s at Lawrence Livermore National Laboratory.[9]

UV solar cells and UV degradation of solar cells

Japan's National Institute of Advanced Industrial Science and Technology (AIST) has succeeded in developing a transparent solar cell that uses ultraviolet light to generate electricity but allows visible light to pass through it. Most conventional solar cells use visible and infrared light to generate electricity. In contrast, the innovative new solar cell uses ultraviolet radiation. Used to replace conventional window glass, the installation surface area could be large, leading to potential uses that take advantage of the combined functions of power generation, lighting and temperature control.[56]

Also PEDOT-PSS solar cells is an ultraviolet (UV) light-selective and -sensitive photovoltaic cell easily fabricated.[57]

On the other hand, a nanocrystalline layer of Cu2O in the construction of photovoltaic cells increases their ability to utilize UV radiations for photocurrent generation.[58]

Nondestructive testing

UV light of a specified spectrum and intensity is used to stimulate fluorescent dyes so as to highlight defects in a broad range of materials. These dyes may be carried into surface-breaking defects by capillary action (liquid penetrant inspection) or they may be bound to ferrite particles caught in magnetic leakage fields in ferrous materials (magnetic particle inspection).

Evolutionary significance

Evolution of early reproductive proteins and enzymes is attributed in modern models of evolutionary theory to ultraviolet light. UVB light causes thymine base pairs next to each other in genetic sequences to bond together into thymine dimers, a disruption in the strand that reproductive enzymes cannot copy (see picture above). This leads to frameshifting during genetic replication and protein synthesis, usually killing the organism. As early prokaryotes began to approach the surface of the ancient oceans, before the protective ozone layer had formed, blocking out most wavelengths of UV light, they almost invariably died out. The few that survived had developed enzymes that verified the genetic material and broke up thymine dimer bonds, known as base excision repair enzymes. Many enzymes and proteins involved in modern mitosis and meiosis are similar to excision repair enzymes, and are believed to be evolved modifications of the enzymes originally used to overcome UV light.[59]

See also


  1. ^ 08 November 2011. "HPS.org". HPS.org. http://www.hps.org/publicinformation/ate/q2111.html. Retrieved 2011-11-08. 
  2. ^ Hockberger, P. E. (2002). "A history of ultraviolet photobiology for humans, animals and microorganisms". Photochem. Photobiol. 76 (6): 561–579. doi:10.1562/0031-8655(2002)076<0561:AHOUPF>2.0.CO;2. PMID 12511035. http://www.bioone.org/doi/abs/10.1562/0031-8655%282002%29076%3C0561%3AAHOUPF%3E2.0.CO%3B2. 
  3. ^ The ozone layer protects humans from this. Lyman, T. (1914). "Victor Schumann". Astrophysical Journal 38: 1–4. Bibcode 1914ApJ....39....1L. doi:10.1086/142050. 
  4. ^ "ISO 21348 Process for Determining Solar Irradiances". http://www.spacewx.com/ISO_solar_standard.html. 
  5. ^ "Ozone layer". http://www.nas.nasa.gov/About/Education/Ozone/ozonelayer.html. Retrieved 2007-09-23. 
  6. ^ "Soda Lime Glass Transmission Curve". http://www.sinclairmfg.com/datasheets/sodalimecurve.htm. 
  7. ^ "B270-Superwite Glass Transmission Curve". http://www.pgo-online.com/intl/katalog/curves/B270_kurve.html. 
  8. ^ "Selected Float Glass Transmission Curve". http://www.pgo-online.com/intl/katalog/curves/whitefl_kurve.html. 
  9. ^ a b Marshall, Chris (1996). "A simple, reliable ultraviolet laser: the Ce:LiSAF". Lawrence Livermore National Laboratory. https://www.llnl.gov/str/Marshall.html. Retrieved 2008-01-11. 
  10. ^ Klose, Jules Z.; Bridges, J. Mervin; Ott, William R. (June 1987). "NBS Measurement Services: Radiometric Standards in the VUV" (PDF). NBS Special publication (US Dept. of Commerce) (250-3). http://ts.nist.gov/MeasurementServices/Calibrations/upload/SP250-3.pdf. 
  11. ^ "Gullikson, Korde, Canfield, Vest, " Stable Silicon Photodiodes for absolute intensity measurements in the VU V and soft x-ray regions", Jrnl of Elec. Spect. and Related Phenomena 80(1996) 313-316". Ts.nist.gov. http://ts.nist.gov/MeasurementServices/Calibrations/upload/JES-80.PDF. Retrieved 2011-11-08. 
  12. ^ "Oregon State University". Lpi.oregonstate.edu. http://lpi.oregonstate.edu/infocenter/vitamins/vitaminD/. Retrieved 2011-11-08. 
  13. ^ Dawe, R.S.; et al (27 June 2003). "A randomized controlled trial of narrowband ultraviolet B vs. bath-psoralen plus ultraviolet A photochemotherapy for psoriasis". British Journal of Dermatology (London: British Association of Dermatologists) 148 (6): 1194–1204. doi:10.1046/j.1365-2133.2003.05482.x. PMID 12828749. 
  14. ^ Kirke, Sandra M; et al (22 March 2007). "A Randomized Comparison of Selective Broadband UVB and Narrowband UVB in the Treatment of Psoriasis". Journal of Investigative Dermatology (Cleveland, OH: Society for Investigative Dermatology) 127 (7): 1641–1646. doi:10.1038/sj.jid.5700767. ISSN 0022-202X. PMID 17380117. 
  15. ^ Davies H.; Bignell G. R.; Cox C.; (June 2002). "Mutations of the BRAF gene in human cancer". Nature 417 (6892): 949–954. doi:10.1038/nature00766. PMID 12068308. http://www.nature.com/nature/journal/v417/n6892/full/nature00766.html. 
  16. ^ "Health effects of UV radiation". http://www.who.int/uv/health/en/. 
  17. ^ C.Michael Hogan. 2011. Sunlight. eds. P.saundry & C.Cleveland. Encyclopedia of Earth.
  18. ^ Matsumu, Y.; Ananthaswamy, H. N. (2004). "Toxic effects of ultraviolet radiation on the skin". Toxicology and Applied Pharmacology 195 (3): 298–308. doi:10.1016/j.taap.2003.08.019. PMID 15020192. 
  19. ^ Torma, H; Berne, B; Vahlquist, A (1988). "UV irradiation and topical vitamin A modulate retinol esterification in hairless mouse epidermis". Acta Derm. Venereol. 68 (4): 291–299. PMID 2459873. 
  20. ^ a b Autier P; Dore J F; Schifflers E; et al. (1995). "Melanoma and use of sunscreens: An EORTC case control study in Germany, Belgium and France". Int. J. Cancer 61 (6): 749–755. doi:10.1002/ijc.2910610602. PMID 7790106. 
  21. ^ a b Hanson Kerry M.; Gratton Enrico; Bardeen Christopher J. (2006). "Sunscreen enhancement of UV-induced reactive oxygen species in the skin". Free Radical Biology and Medicine 41 (8): 1205–1212. doi:10.1016/j.freeradbiomed.2006.06.011. PMID 17015167. 
  22. ^ a b R. Bissonnette, MD, FRCPC, Innovaderm Research, Montreal, QC, Canada, Update on Sunscreens
  23. ^ a b Xu, C.; Green, Adele; Parisi, Alfio; Parsons, Peter G (2001). "Photosensitization of the Sunscreen Octyl p-Dimethylaminobenzoate b UVA in Human Melanocytes but not in Keratinocytes.". Photochemistry and Photobiology 73 (6): 600–604. doi:10.1562/0031-8655(2001)073<0600:POTSOP>2.0.CO;2. PMID 11421064. 
  24. ^ a b Knowland, John; McKenzie, Edward A.; McHugh, Peter J.; Cridland, Nigel A. (1993). "Sunlight-induced mutagenicity of a common sunscreen ingredient.". FEBS Letters 324 (3): 309–313. doi:10.1016/0014-5793(93)80141-G. PMID 8405372. 
  25. ^ a b Damiani, E.; Greci, L.; Parsons, R.; Knowland (1999). "Nitroxide radicals protect DNA from damage when illuminated in vitro in the presence of dibenzoylmethane and a common sunscreen ingredient.". Free Radic. Biol. Med. 26 (7-8): 809–816. doi:10.1016/S0891-5849(98)00292-5. PMID 10232823. 
  26. ^ Chatelaine, E.; Gabard, B.; Surber, C. (2003) pdf Skin Penetration and Sun Protection Factor of Five UV Filters: Effect of the Vehicle, Skin Pharmacol. Appl. Skin Physiol., 16:28-35 DOI: 10.1159/000068291
  27. ^ a b c d e f g European Guidelines for Photodermatoses > 2 Photoaggravated Disorders at European Dermatology Forum
  28. ^ Nolan, T. M. et al. (2003). "The Role of Ultraviolet Irradiation and Heparin-Binding Epidermal Growth Factor-Like Growth Factor in the Pathogenesis of Pterygium". American Journal of Pathology (American Journal of Pathology) 162 (2): 567–74. doi:10.1016/S0002-9440(10)63850-3. PMC 1851157. PMID 12547714. http://ajp.amjpathol.org/cgi/content/abstract/162/2/567. 
  29. ^ Di Girolamo, N. et al. (1 August 2005). "Epidermal Growth Factor Receptor Signaling Is Partially Responsible for the Increased Matrix Metalloproteinase-1 Expression in Ocular Epithelial Cells after UVB Radiation". American Journal of Pathology 167 (2): 489–503. doi:10.1016/S0002-9440(10)62992-6. PMC 1603570. PMID 16049334. http://ajp.amjpathol.org/cgi/content/abstract/167/2/489. 
  30. ^ R. V. Lapshin, A. P. Alekhin, A. G. Kirilenko, S. L. Odintsov, V. A. Krotkov (2010). "Vacuum ultraviolet smoothing of nanometer-scale asperities of poly(methyl methacrylate) surface" (PDF). Journal of Surface Investigation. X-ray, Synchrotron and Neutron Techniques (Russia: Pleiades Publishing) 4 (1): 1–11. doi:10.1134/S1027451010010015. ISSN 1027-4510. http://www.nanoworld.org/homepages/lapshin/publications.htm#vacuum2010.  (Russian translation is available).
  31. ^ s-et.com[dead link]
  32. ^ "Ultraviolet Light, UV Rays, What is Ultraviolet, UV Light Bulbs, Fly Trap". Pestproducts.com. http://www.pestproducts.com/uv_light.htm. Retrieved 2011-11-08. 
  33. ^ "Pepper Spray FAQ". http://www.worthprotectionsecurity.com/how-to-use-pepper-spray.htm. 
  34. ^ Anja Fiedler, Mark Benecke et al.. "Detection of Semen (Human and Boar) and Saliva on Fabrics by a Very High Powered UV-/VIS-Light Source". http://wiki.benecke.com/index.php?title=2008_The_Open_Forensic_Science_Journal:_Detection_of_Semen_%28Human_and_Boar%29_and_Saliva_on_Fabrics_by_a_Very_High_Powered_UV-/VIS-Light_Source. Retrieved 2009-12-10. 
  35. ^ Scott, K.J.; Wills, R.R.H.; Patterson, B.D. (1971). Journal of the Science of Food and Agriculture (22): 496–7. 
  36. ^ Scott, KJ; Wills, RBH (1973). "Atmospheric pollutants destroyed in an ultra violet scrubber.". Laboratory Practice 22 (2): 103–6. PMID 4688707. 
  37. ^ Shorter, AJ; Scott, KJ (1986). Lebensm-Wiss u Technology 19: 176–9. 
  38. ^ "UV is used to treat tuberculosis of the skin". Nobelprize.org. 1903-12-10. http://nobelprize.org/nobel_prizes/medicine/laureates/1903/press.html. Retrieved 2011-11-08. 
  39. ^ "UVB Phototherapy" (php). National Psoriasis Foundation, USA. Archived from the original on 2007-06-22. http://web.archive.org/web/20070622180124/http://www.psoriasis.org/treatment/psoriasis/phototherapy/uvb.php. Retrieved 2007-09-23. 
  40. ^ Black, R.J.; Gavin, A.T. (2006). "Photocarcinogenic risk of narrowband ultraviolet B (TL-01) phototherapy: early follow-up data.". BJD (154): 551–7. 
  41. ^ "Deep UV Photoresists". http://www.almaden.ibm.com/st/chemistry/lithography/deep_uv/. 
  42. ^ "Corona - The Daytime UV Inspection Magazine". http://www.seeing-corona.com/. 
  43. ^ "Municipal Drinking Water: Multi-barrier Disinfection Strategy - New York City". Trojan Technologies. http://trojanuv.com/uvresources?resource=403. Retrieved 19 September 2011. 
  44. ^ "Groundwater Replenishment System - Orange County". Trojan Technologies. http://trojanuv.com/uvresources?resource=44. 
  45. ^ "New Purification Plant Answers California's Water Crisis". Wired.com. http://www.wired.com/science/planetearth/multimedia/2008/01/gallery_sewage_plant. Retrieved 2011-11-08. 
  46. ^ Antoniou, Maria G.; Dionysiou, Dionysios D. (30 June 2007). "Application of immobilized titanium dioxide photocatalysts for the degradation of creatinine and phenol, model organic contaminants found in NASA's spacecrafts wastewater streams". Catalysis Today (Elsevier) 124 (3-4): 215–223. doi:10.1016/j.cattod.2007.03.054. 
  47. ^ Ware, M. W. et al. (PDF). Inactivation of Giardia muris by Low Pressure Ultraviolet Light. United States Environmental Protection Agency. Archived from the original on February 27, 2008. http://web.archive.org/web/20080227143624/http://www.epa.gov/nerl/news/forum2003/water/ware_poster.pdf. Retrieved 2008-12-28. 
  48. ^ "Solar Water Disinfection". Sodis.ch. 2011-04-02. http://www.sodis.ch/index.htm. Retrieved 2011-11-08. 
  49. ^ Rulfsorchard.com
  50. ^ Nita Agar; Antony R. Young (2005). "Review: Melanogenesis: a photoprotective response to DNA damage?". Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis 571 (1-2): 121–132. doi:10.1016/j.mrfmmm.2004.11.016. PMID 15748643. 
  51. ^ Garland C, Garland F, Gorham E (1992). "Could sunscreens increase melanoma risk?". Am J Public Health 82 (4): 614–5. doi:10.2105/AJPH.82.4.614. PMC 1694089. PMID 1546792. http://www.ajph.org/cgi/reprint/82/4/614. 
  52. ^ Westerdahl J; Ingvar C; Masback A; Olsson H (2000). "Sunscreen use and malignant melanoma.". International journal of cancer. Journal international du cancer 87 (1): 145–50. doi:10.1002/1097-0215(20000701)87:1<145::AID-IJC22>3.0.CO;2-3. PMID 10861466. 
  53. ^ Weinstock, M. A. (1999). "Do sunscreens increase or decrease melanoma risk: An epidemiologic evaluation.". Journal of Investigative Dermatology Symposium Proceedings 4 (1): 97–100. PMID 10537017. 
  54. ^ Vainio, H., Bianchini, F. (2000). "Cancer-preventive effects of sunscreens are uncertain.". Scandinavian Journal of Work Environment and Health 26: 529–31. 
  55. ^ "Digital Photography of Documents". wells-geneaology.org.uk. http://www.wells-genealogy.org.uk/photography.htm. 
  56. ^ "Japanfs.org". Japanfs.org. http://www.japanfs.org/en/pages/025337.html. Retrieved 2011-11-08. 
  57. ^ "AIP.org". Scitation.aip.org. http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=APPLAB000083000011002097000001&idtype=cvips&gifs=yes. Retrieved 2011-11-08. 
  58. ^ "Photovoltaic cell using stable Cu2O nanocrystals and conductive polymers - Patent 6849798". Freepatentsonline.com. 2002-12-17. http://www.freepatentsonline.com/6849798.html. Retrieved 2011-11-08. 
  59. ^ Margulis, Lynn and Sagan, Dorion (1986) (book). Origins of Sex: Three Billion Years of Genetic Recombination. 1. Yale University Press. ISBN 9780300046199. http://books.google.com/?id=3hDVTEk3ioIC&pg=PP1&lpg=PP1&dq=origins+of+sex:+three. 

Further reading

Wikimedia Foundation. 2010.

Игры ⚽ Поможем решить контрольную работу

Look at other dictionaries:

  • ULTRAVIOLET — L’ultraviolet est le domaine des radiations électromagnétiques s’étendant depuis la limite violette du spectre visible (400 nm) jusqu’à la région des rayons X mous, qu’il recouvre partiellement (cf. figure). Cette délimitation repose… …   Encyclopédie Universelle

  • UltraViolet — es un Sistema de Derechos digitales (DRM) basado en la nube, desarrollado por DECE LLC, un consorcio que incluye a Sony, Adobe, Cisco, HP, Microsoft e Intel.[1] [2] Apple y Disney no soportan este formato.[3] UltraViolet pretende cr …   Wikipedia Español

  • ultraviolet — ULTRAVIOLÉT, Ă, ultravioleţi, te, adj. (Despre radiaţiile electromagnetice; şi substantivat, f. pl.) Care are lungimea de undă mai mică decât lungimea de undă minimă a radiaţiilor vizibile. [pr.: vi o ] – Din fr. ultraviolet. Trimis de ana… …   Dicționar Român

  • Ultraviolet — (engl. für ultraviolett) steht für: Ultraviolettstrahlung (UV Licht), elektromagnetische Strahlung Ultraviolet (Film) (2006), einen Science Fiction Thriller UltraViolet Ist ein Video Standard für eine Cloud Basierte Speicherung und Wiedergabe mit …   Deutsch Wikipedia

  • Ultraviolet — Ul tra*vi o*let, a. [Pref. ultra + violet.] (Physics) Lying outside the visible spectrum at its blue violet end; said of light more refrangible (i. e. having a shorter wavelength) than the extreme violet rays of the visible spectrum.… …   The Collaborative International Dictionary of English

  • ultraviolet — [ul΄trə vī′ə lit] adj. 1. pertaining to a band of electromagnetic radiation having wavelengths (from c. 5 to c. 400 nanometers) that are shorter than violet light 2. of, pertaining to, or producing radiation of such wavelengths n. ultraviolet… …   English World dictionary

  • ultraviolet — beyond the violet end of the visible spectrum, 1840, from ULTRA (Cf. ultra ) + VIOLET (Cf. violet). Ultra red (1870) was a former name for what now is called infra red …   Etymology dictionary

  • ultraviolet — ► NOUN ▪ electromagnetic radiation having a wavelength just shorter than that of violet light but longer than that of X rays. ► ADJECTIVE ▪ denoting such radiation …   English terms dictionary

  • Ultraviolet A — One of the three types of invisible light rays (together with ultraviolet B and ultraviolet C) given off by the sun. Although ultraviolet C is the most dangerous type of ultraviolet light in terms of its potential to harm life on earth, it cannot …   Medical dictionary

  • Ultraviolet B — One of the three types of invisible light rays (together with ultraviolet A and ultraviolet C) given off by the sun. Although ultraviolet C is the most dangerous type of ultraviolet light in terms of its potential to harm life on earth, it cannot …   Medical dictionary

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”