See Also

Ultraviolet

Ultraviolet light is electromagnetic radiation Electromagnetic radiation

Electromagnetic radiation is generally described as a self-propagating wave [i] in space with electric [i] ... 

 with a wavelength Wavelength

The wavelength is the distance between repeating units of a wave [i] pattern. ... 

 shorter than that of visible light, but longer than soft X-ray X-ray

X-rays are a form of electromagnetic radiation [i] with a wavelength [i] in the range of 10 to 0.01 nanometre [i] ... 

s. It can be subdivided into near UV , far or vacuum UV , and extreme UV . When considering the effect of UV radiation on human health and the environment, the range of UV wavelengths is often subdivided into UVA , also called Long Wave or "blacklight"; UVB , also called Medium Wave; and UVC , also called Short Wave or "germicidal". See 1 E-7 m for a list of objects of comparable sizes. In photolithography Photolithography

Photolithography or optical lithography is a process used in semiconductor device fabrication [i] ... 

, in laser Laser

A laser is an optical source that emits photons [i] in a coherent [i] beam. ... 

 technology, etc., the term deep ultraviolet or DUV refers to wavelengths below 300 nm.

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Timeline

1801   The ultraviolet radiation Ultraviolet

Ultraviolet light is electromagnetic radiation [i] with a wavelength [i] shorter than that of visible l ... 

 is discovered by Johann Wilhelm Ritter.



Encyclopedia

Ultraviolet light is electromagnetic radiation Electromagnetic radiation

Electromagnetic radiation is generally described as a self-propagating wave [i] in space with electric [i] ... 

 with a wavelength Wavelength

The wavelength is the distance between repeating units of a wave [i] pattern. ... 

 shorter than that of visible light, but longer than soft X-ray X-ray

X-rays are a form of electromagnetic radiation [i] with a wavelength [i] in the range of 10 to 0.01 nanometre [i] ... 

s. It can be subdivided into near UV , far or vacuum UV , and extreme UV .

When considering the effect of UV radiation on human health and the environment, the range of UV wavelengths is often subdivided into UVA , also called Long Wave or "blacklight"; UVB , also called Medium Wave; and UVC , also called Short Wave or "germicidal". See 1 E-7 m for a list of objects of comparable sizes.

In photolithography Photolithography

Photolithography or optical lithography is a process used in semiconductor device fabrication [i] ... 

, in laser Laser

A laser is an optical source that emits photons [i] in a coherent [i] beam. ... 

 technology, etc., the term deep ultraviolet or DUV refers to wavelengths below 300 nm.

The name means "beyond violet" , violet being the color Color

Color or colour is the visual perceptual property corresponding in humans to the categories... 

 of the shortest wavelengths of visible light. Some of the UV wavelengths are colloquially called black light, as it is invisible to the human eye. Some animals, including bird Bird

Birds are biped [i]al, warm-blooded [i], oviparous [i] vertebrate [i] animals characterized [i] ... 

s, reptile Reptile

Reptiles are tetrapod [i]s and amniote [i]s, animals whose embryo [i]s are surrounded by an amniotic membrane [i] ... 

s, and insect Insect

Insects are invertebrate [i]s that are taxonomically [i] referred to as the class Inse ... 

s such as bee Bee

Bees are flying insect [i]s, closely related to wasp [i]s and ant [i]s. ... 

s, can see into the near ultraviolet. 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. Many birds have patterns in their plumage that are invisible at usual wavelengths but observable in ultraviolet, and the urine of some animals is much easier to spot with ultraviolet.

The Sun Sun

|+ The Sun   |+
|-
... 

 emits ultraviolet radiation in the UVA, UVB, and UVC bands, but because of absorption in the atmosphere Earth's atmosphere

Earth's atmosphere is a layer of gases surrounding the planet Earth [i] and retained by the Earth's gravity [i]... 

's ozone layer Ozone layer

The ozone layer, or ozonosphere layer , is that part of the Earth's atmosphere [i] which contains ... 

, 99% of the ultraviolet radiation that reaches the Earth's surface is UVA.

Ordinary glass Glass

Glass is a uniform amorphous solid [i] material, usually produced when the viscous molten material cools ... 

 is partially transparent to UVA but is opaque to shorter wavelengths while 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.

The onset of vacuum UV, 200 nm, is defined by the fact that ordinary air is opaque below this wavelength. This opacity is due to the strong absorption of light of these wavelengths by oxygen in the air. Pure nitrogen is transparent to wavelengths in the range of about 150–200 nm. This has wide practical significance now that semiconductor manufacturing processes are 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, such as circular dichroism Circular dichroism

Circular dichroism, is the differential absorption of left- and right-handed circularly polarized [i] ... 

 spectrometers, are also commonly nitrogen purged and operate in this spectral region.

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 Valence electron

In chemistry [i], valence electrons are the electrons [i] located within the outermost energy level of a ... 

 of matter, while wavelengths shorter than that interact mainly with inner shell electrons and nuclei. The long end of the EUV/XUV spectrum is set by a prominent He+ Helium

|-
| 3He || 0.000137%* || colspan="4" | He is stable [i] with 1 neutron [i]
... 

 spectral line Spectral line

A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum [i] ... 

 at 30.4nm. 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 Angle of incidence

An angle of incidence is the angle between a beam incident on a surface and the line perpendicular to th... 

. This technology has been used to make telescopes for solar imaging Sun

|+ The Sun   |+
|-
... 

; it was pioneered by the NIXT and MSSTA MSSTA

The Multi-spectral solar telescope array, or MSSTA, was a sounding rocket [i] payload built by Pro ... 

 sounding rockets in the 1990s; current examples are SOHO Solar and Heliospheric Observatory

The Solar and Heliospheric Observatory is a spacecraft [i] that was launched on 2 December [i] 1995 [i] ... 

/EIT and TRACE) and for nanolithography .


Discovery


Soon after infrared Infrared

Infrared radiation is electromagnetic radiation [i] of a wavelength [i] longer than that of visible light [i] ... 

 radiation had been discovered, the German physicist Johann Wilhelm Ritter began to look for radiation at the opposite end of the spectrum, at the short wavelengths beyond violet. In 1801 he used silver chloride Silver chloride

Silver chloride chloride) is a chemical compound [i] with chemical formula [i] AgCl and is composed o ... 

, a light-sensitive chemical, to show that there was a type of invisible light beyond violet, which he called chemical rays. At that time, many scientists, including Ritter, concluded that light was composed of three separate components: an oxidising or calorific component , an illuminating component , and a reducing or hydrogenating component . The unity of the different parts of the spectrum was not understood until about 1842, with the work of Macedonio Melloni, Alexandre-Edmond Becquerel A. E. Becquerel

Alexandre-Edmond Becquerel was a French [i] physicist [i] who studied the solar spectrum [i], magnetism [i] ... 

 and others. During that time, UV radiation was also called "actinic radiation".

Health concerns and protection


In humans, prolonged exposure to solar UV radiation may result in acute and chronic health effects on the skin Skin

In zootomy [i] and dermatology [i], skin is an organ [i] of the integumentary system [i] made up ... 

, eye, and immune system Immune system

The immune system is composed of a complex constellation of cells, organs and tissues, arranged in an el... 

.

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 Earth's atmosphere

Earth's atmosphere is a layer of gases surrounding the planet Earth [i] and retained by the Earth's gravity [i]... 

. 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.


Skin



UVA, UVB and UVC can all damage collagen Collagen

Collagen is the main protein [i] of connective tissue [i] in animal [i]s and the most abundant protein i ... 

 fibers and thereby accelerate aging of the skin. In general, UVA is the least harmful, but can contribute to the aging of skin, DNA damage and possibly skin cancer. It penetrates deeply and does not cause sunburn Sunburn

A sunburn is a burn [i] to the skin [i] produced by overexposure to ultraviolet [i] radiation, comm ... 

. Because it does not cause reddening of the skin it cannot be measured in the SPF Sunscreen

Sunscreen is a lotion [i], spray or other topical [i] product that helps protect the skin from the sun [i]... 

 testing. There is no good clinical measurement of the blocking of UVA radiation, but it is important that sunscreen Sunscreen

Sunscreen is a lotion [i], spray or other topical [i] product that helps protect the skin from the sun [i]... 

 block both UVA and UVB.

UVA light is also known as "dark-light" and, because of its longer wavelength, can penetrate most windows. It also penetrates deeper into the skin than UVB light and is thought to be a prime cause of wrinkle Wrinkle

A wrinkle is a ridge [i] or crease of a surface. ... 

s.

UVB light can cause skin cancer Skin cancer

Skin cancer is a malignant [i] growth on the skin [i], which can have many causes, including repeated se ... 

. The radiation excites DNA DNA

Deoxyribonucleic acid is a nucleic acid [i] that contains the genetic [i] instructions for t... 

 molecules in skin cells, causing covalent bond Covalent bond

Covalent bonding is an intramolecular form of chemical bond [i]ing characterized by the sharing of one o ... 

s to form between adjacent thymine Thymine

... 

 bases, producing thymidine dimers. Thymidine dimers do not base pair normally, which can cause distortion of the DNA helix, stalled replication, gaps, and misincorporation. These can lead to mutations, which can result in cancer Cancer

Cancer is a class of disease [i]s or disorders characterized by uncontrolled division [i] ... 

ous growths. The mutagenicity of UV radiation can be easily observed in bacteria Bacteria

Bacteria are a major group of living organism [i]s. ... 

 cultures. This cancer connection is one reason for concern about ozone depletion Ozone depletion

The term ozone depletion is used to describe two distinct but related observations: a slow, steady d... 

 and the ozone hole.

As a defense against UV radiation, the body tans when exposed to moderate levels of radiation by releasing the brown pigment melanin Melanin

Broadly, melanin is any of the polyacetylene [i], polyaniline [i], and polypyrrole [i] "blacks" and "bro ... 

. This helps to block UV penetration and prevent damage to the vulnerable skin tissues deeper down. Suntan lotion that partly blocks UV is widely available . Most of these products contain an "SPF rating" that describes the amount of protection given. This protection, however, applies only to UVB rays responsible for sunburn and not to UVA rays that penetrate more deeply into the skin and may also be responsible for causing cancer and wrinkles. Some sunscreen lotion now includes compounds such as titanium dioxide which helps protect against UVA rays. Other UVA blocking compounds found in sunscreen include zinc oxide and avobenzone. There are also naturally occurring compounds found in rainforest plants that have been known to protect the skin from UV radiation damage, such as the fern Polypodium leucotomos.

What to look for in sunscreen:

UVB protection: Padimate O Padimate O

Padimate O is an organic compound [i] that is an ingredient in some sunscreen [i]s. ... 

, Homosalate Homosalate

Homosalate is an organic compound [i] used in some sunscreen [i]s.... 

, Octisalate , Octinoxate

UVA protection: Avobenzone Avobenzone

[i] and [[UVB]... 



UVA/UVB protection: Octocrylene Octocrylene

Octocrylene is an organic compound [i] used as an ingredient in sunscreen [i]s and cosmetics. ... 

, titanium dioxide Titanium dioxide

Titanium dioxide, also known as titanium(IV) oxide or titania, is the naturally occurring oxide [i]... 

, zinc oxide Zinc oxide

Zinc oxide is a chemical compound [i] with formula ZnO. ... 

, Mexoryl

Eye

High intensities of UVB light are hazardous to the eyes, and exposure can cause welder's flash and may lead to cataract Cataract

A cataract is an opacity [i] that develops in the, crystalline lens [i] of the eye [i] or in its en ... 

s, pterygium  , and pinguecula formation.

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 Glasses

Glasses, spectacles, or eyeglasses are frames bearing lenses [i] worn below the forehea ... 

 give some protection. Most plastic lenses give more protection than glass lenses, because, as noted above, glass is transparent to UVA and the common acrlyic plastic used for lenses is less so. Some plastic lens materials, such as polycarbonate Polycarbonate

h colspan="2" align=center bgcolor="#cccccc">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. To convince yourself of the potential dangers of stray UV light, cover your lenses with something opaque, like aluminum foil, stand next to a bright light, and consider how much light you see, despite the complete blockage of the lenses. Most intraocular lenses help to protect the retina Retina

The retina is a thin layer of neural cells that lines the back of the eye [i]ball of vertebrate [i]s and ... 

 by absorbing UV radiation.

Beneficial effects

A positive effect of UV light is that it induces the production of vitamin D Vitamin D

[i] precursor that contributes to the maintenance of normal levels of [[calcium]... 

 in the skin. claims tens of thousands of premature deaths occur in the US annually from cancer due to insufficient UVB exposures . Another effect of vitamin D deficiency is osteomalacia , which can result in bone pain, difficulty in weight bearing and sometimes fractures.

Ultraviolet radiation has other medical applications, in the treatment of skin conditions such as psoriasis Psoriasis

Psoriasis is an immune-mediated disease [i]
... 

 and vitiligo Vitiligo

Vitiligo or leukoderma is a chronic skin disease that causes loss of pigment, resulting in irregu... 

. UVB and UVA radiation can be used, in conjunction with psoralens .

Most effective in case of psoriasis and vitiligo is UV light with wavelength of 311 nm.

Uses


Black lights


A black light Black light

Black light is the common name for a lamp [i] emitting electromagnetic radiation [i] that is almost excl ... 

 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 only one phosphor is used and the normally clear glass envelope of the bulb is replaced by a deep bluish purple glass called Wood's glass Wood's glass

Wood's glass was developed by Robert Williams Wood [i] as a light filter used in communications during World War I [i] ... 

.

To thwart counterfeiters Counterfeit

A counterfeit is an imitation that is made usually with the intent to deceptively represent its content ... 

, sensitive documents may also include a UV watermark that can only be seen when viewed under a UV-emitting light. Passports issued by most countries usually contain UV sensitive inks and security threads. Visa stamps and stickers such as those issued by Ukraine contain large and detailed seals invisible to the naked eye under normal lights, but strongly visible under UV illimunation. Passports issued by the United States have the UV sensitive threads on the last page of the passport along with the barcode.

Fluorescent lamps

Fluorescent lamp Fluorescent lamp

A fluorescent lamp is a gas-discharge lamp [i] that uses electricity [i] to excite mercury [i] vapor [i] ... 

s 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 lamp Xenon flash lamp

A xenon flash lamp is an electric glow discharge [i] lamp designed to produce extremely intense, incoherent [i] ... 

s , deuterium arc lamps, mercury-xenon arc lamps, metal-halide arc lamps, and tungsten-halogen incandescent lamps.

Astronomy


In astronomy Astronomy

Astronomy is the science [i] of celestial objects and phenomena [i] that originate outside the Earth's atmosphere [i] ... 

, very hot objects preferentially emit UV radiation . However, the same ozone layer that protects us causes difficulties for astronomers observing from the Earth, so most UV observations are made from space.

Pest control

Ultraviolet fly traps are used for the elimination of various small flying insects. They are attracted to the UV light and are killed using an electrical shock or trapped once they come into contact with the device.

Spectrophotometry

UV/VIS spectroscopy Ultraviolet-visible spectroscopy

Ultraviolet-visible spectroscopy or ultraviolet-visible spectrophotometry involves the spectroscopy [i] ... 

 is widely used as a technique in chemistry Chemistry

Chemistry is the science [i] of matter [i] at the atom [i]ic to molecular [i] scale, dealing primarily ... 

, for analysis of chemical structure, most notably conjugated system Conjugated system

A chemically conjugated system is a system of atoms covalent [i]ly bonded [i] with alterna ... 

s. UV radiation is often used in visible spectrophotometry Spectrophotometry

In physics [i], spectrophotometry is the quantitative study of electromagnetic spectra [i] ... 

 to determine the existence of fluorescence a given sample.

Analyzing minerals



Ultraviolet lamps are also used in analyzing minerals Mineral

Minerals are natural compounds formed through geological [i] processes. ... 

, gems Gemstone

A gemstone is a mineral [i], rock [i] , or petrified [i] material that when cut or f ... 

, and in other detective work including authentication of various collectibles. Materials may look the same under visible light, but fluoresce Fluorescence

Fluorescence is a luminescence [i] that is mostly found as an optical phenomenon [i] in cold bodies, in ... 

 to different degrees under ultraviolet light; or may fluoresce differently under short wave ultraviolet versus long wave ultraviolet. UV fluorescent dye Dye

A dye can generally be described as a color [i]ed substance that has an affinity [i] t ... 

s are used in many applications . The fluorescent protein Protein

Proteins are large organic compound [i]s made of amino acid [i]s arranged in a linear chain and joined b ... 

 Green Fluorescent Protein Green fluorescent protein

The green fluorescent protein is a protein [i] from the jellyfish [i] Aequorea victoria [i] that fluoresces [i] ... 

  is often used in genetics as a marker. Many substances, proteins for instance, 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.

Photolithography

Ultraviolet radiation is used for very fine resolution photolithography Photolithography

Photolithography or optical lithography is a process used in semiconductor device fabrication [i] ... 

, a procedure where a chemical known as a photoresist is exposed to UV radiation which has passed through a mask. The light allows chemical reactions to take place in the photoresist, and after development , a geometric pattern which is determined by the mask remains on the sample. Further steps may then be taken to "etch" away parts of the sample with no photoresist remaining.

UV radiation is used extensively in the electronics industry because photolithography is used in the manufacture of semiconductor Semiconductor

A semiconductor is a material with electrical conductivity [i] that is intermediate between that of an ... 

s, integrated circuit Integrated circuit

A monolithic integrated circuit is a miniaturized electronic circuit [i] which has been manufactured i ... 

 components and printed circuit board Printed circuit board

In electronics [i], printed circuit boards, or PCBs, are used to mechanically support and el ... 

s.

Checking electrical insulation

A new application of UV is to detect corona discharge  on electrical apparatus. Degradation of insulation of 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 Ozone

Ozone is a triatomic molecule [i], consisting of three oxygen atom [i]s. ... 

 and to a lesser extent nitrogen oxide which may subsequently react with water in the air to form nitrous acid Nitrous acid

Nitrous acid is a weak monobasic acid [i] known only in solution [i] and in the form of nitrite [i] salt ... 

 and nitric acid Nitric acid

The chemical compound [i] nitric acid , otherwise known as aqua fortis or spirit of nitre, i ... 

 vapour in the surrounding air.

Sterilization



Ultraviolet lamps are used to sterilize workspaces and tools used in biology laboratories and medical facilities. Commercially-available low pressure mercury-vapor lamps Mercury-vapor lamp

A Mercury-vapor lamp is a gas discharge [i] lamp [i] which uses mercury [i] in an excited state ... 

 emit about 86% of their light at 254 nanometers which coincides very well with one of the two peaks of the germicidal effectiveness curve . 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 . UV light at these germicidal wavelengths causes adjacent thymine Thymine

... 

 molecules on DNA to dimer Dimer

... 

ize, if enough of these defects accumulate on a microorganism's DNA its replication is inhibited, thereby rendering it harmless . Since microorganisms can be shielded from ultraviolet light in small cracks and other shaded areas, however, 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 was more commonly used in wastewater treatment applications but is finding increased usage in drinking water treatment. 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 which have outer coatings or that form cyst states 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 Cryptosporidium

Cryptosporidium is a protozoan pathogen of the Phylum Apicomplexa [i] and causes a diarrhea [i]l illness ... 

. The findings resulted in two and 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. It turns out that protists Protist

Protists are a heterogeneous [i] group of organisms, comprising those eukaryote [i]s that are not animal [i] ... 

 are able to survive high UV-C doses but are sterilized at low doses.

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 Foodborne illness

A foodborne illness, also foodborne disease and commonly called food poisoning, is any illness [i] ... 

 is also raising demand for improved food processing methods. Ultraviolet radiation is used in several food processes to remove unwanted microorganisms Microorganism

A microorganism or microbe is an organism [i] that is microscopic [i] . ... 

. UV light can be used to pasteurize fruit juices by flowing the juice over a high intensity ultraviolet light source. The effectiveness of such a process depends on the UV absorbance of the juice .

Fire detection

Ultraviolet detectors generally use either a solid-state device, such as one based on silicon carbide Silicon carbide

| Silicon carbide
|-
| align="center" colspan="2" | |-
... 

 or aluminum nitride Aluminum nitride

Aluminum nitride is a nitride [i] of aluminum [i]. ... 

, or a gas-filled tube as the sensing element. UV detectors which are sensitive to UV light in any part of the spectrum respond to irradiation by sunlight Sunlight

Sunlight in the broad sense is the total spectrum [i] of electromagnetic radiation [i] give ... 

 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, while a coal Coal

Coal is a fossil fuel [i] extracted from the ground by underground mining or open-pit mining . ... 

 fire emits very weakly in the UV band yet very strongly at IR wavelengths; thus a fire detector which 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 UVB band, while the Sun Sun

|+ The Sun   |+
|-
... 

's radiation at this band is absorbed by the Earth's atmosphere Earth's atmosphere

Earth's atmosphere is a layer of gases surrounding the planet Earth [i] and retained by the Earth's gravity [i]... 

. 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 hydrocarbon Hydrocarbon

[i] that consists only of the elements [[carbon]... 

s, metal Metal

In chemistry, a metal is an element [i] that readily forms positive ion [i]s and has ... 

s, sulfur Sulfur

Sulfur or sulphur is the chemical element [i] in the periodic table [i] that has the symbol S' ... 

, hydrogen Hydrogen

|-
| Triple point [i] || 13.8033 K, 7.042 kPa
... 

, hydrazine Hydrazine

Hydrazine is the chemical compound [i] with formula [i] N [i]2H [i]4.... 

, and ammonia Ammonia

Ammonia is a compound [i] of nitrogen [i] and hydrogen [i] with the formula [i] ... 

. Arc welding Arc welding

Arc welding refers to a group of welding [i] processes that use a welding power supply [i] to create an ... 

, electrical arcs, lightning Lightning

Lightning is a powerful natural electrostatic discharge [i] produced during a thunderstorm [i]. ... 

, X-ray X-ray

X-rays are a form of electromagnetic radiation [i] with a wavelength [i] in the range of 10 to 0.01 nanometre [i] ... 

s used in nondestructive metal testing equipment , 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.

Curing of adhesives and coatings

Certain adhesives Adhesive

An adhesive is a compound that adheres [i] or bonds two items together. ... 

 and coatings are formulated with photoinitiators. When exposed to the correct dose and intensity in the required band of UV light, polymerisation 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 Optical fiber

An optical fiber or fibre is a thin, transparent [i] fiber [i], usually made of glass [i]... 

 coatings, the coating of flooring, paper finishes in offset printing, and dental fillings.

Deterring Substance Abuse in Public Restrooms

UV lights have been installed in some parts of the world in public restrooms for the purpose of deterring substance abuse. The blue color of these lights, combined with the fluorescence of the skin, make it harder for intravenous drug users to find a vein. The efficacy of these lights for that purpose has been questioned, with some suggesting that drug users simply find a vein outside the public restroom and mark the spot with a marker for accessibility when inside the restroom. There is currently no published evidence supporting the idea of a deterrent effect.

Erasing EPROM modules

Some EPROM EPROM

An EPROM, or erasable programmable read-only memory [i], is a type of computer memory chip [i] ... 

  modules are erased by exposure to UV radiation. These modules often have a transparent glass window on the top of the chip that allows the UV radiation in. These have been largely superseded by EEPROM and flash memory Flash memory

Flash memory is a form of non-volatile computer memory [i] that can be electrically e ... 

 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 will be greater.

See also

  • UV index
  • High energy visible light
  • Sun tanning Sun tanning

    Sun tanning describes a darkening of the skin in a natural physiological response stimulated by exposure... 

  • Black light Black light

    Black light is the common name for a lamp [i] emitting electromagnetic radiation [i] that is almost excl ... 

  • Wood's lamp

References





External links