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Encyclopedia > UV light

Ultraviolet (UV) radiation is electromagnetic radiation of a wavelength shorter than that of the visible region, but longer than that of soft X-rays. It can be subdivided into near UV (380–200 nm wavelength) and extreme or vacuum UV (200–10 nm). When considering the effects of UV radiation on human health and the environment, the range of UV wavelengths is often subdivided into UVA (380–315 nm), also called Long Wave or "blacklight"; UVB (315–280 nm), also called Medium Wave; and UVC (280-10 nm), also called Short Wave or "germicidal". See 1 E-7 m for a list of objects of comparable sizes. Electromagnetic radiation or EM radiation is a combination (cross product) of oscillating electric and magnetic fields perpendicular to each other, moving through space as a wave, effectively transporting energy and momentum. ... The wavelength is the distance between repeating units of a wave pattern. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... A nanometre (American spelling: nanometer) is 1. ... To help compare different orders of magnitude this page lists lengths between 100 nm and 1 µm (10-7 and 10-6 m). ...


The name means "beyond violet" (from Latin ultra, "beyond"), violet being the color 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 birds, reptiles, and insects such as bees, 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. Many birds have patterns in their plumage that are invisible at usual wavelengths but seen in ultraviolet, and the urine of some animals is much easier to spot with ultraviolet. Latin is the language that was originally spoken in the region around Rome called Latium. ... Violet (named after the flower violet) refers to any of a group of reddish blue or bluish purple colors. ... Color is an important part of the visual arts. ... Diagram of a human eye. ... Orders Many - see section below. ... Orders  Crocodylia - Crocodilians  Rhynchocephalia - Tuataras  Squamata   Suborder Sauria - Lizards   Suborder Serpentes - Snakes Testudines - Turtles Superorder Dinosauria  Saurischia  Ornithischia The reptiles are a group of vertebrate animals. ... Orders Subclass Apterygota Symphypleona - globular springtails Subclass Archaeognatha (jumping bristletails) Subclass Dicondylia Monura - extinct Thysanura (common bristletails) Subclass Pterygota Diaphanopteroidea - extinct Palaeodictyoptera - extinct Megasecoptera - extinct Archodonata - extinct Ephemeroptera (mayflies) Odonata (dragonflies and damselflies) Infraclass Neoptera Blattodea (cockroaches) Mantodea (mantids) Isoptera (termites) Zoraptera Grylloblattodea Dermaptera (earwigs) Plecoptera (stoneflies) Orthoptera (grasshoppers, crickets... Families Andrenidae Anthophoridae Apidae Colletidae Ctenoplectridae Halictidae Heterogynaidae Megachilidae Melittidae Oxaeidae Sphecidae Stenotritidae bee or bees, see bee (disambiguation). ...

The solar corona as seen in "deep" ultraviolet light at 17.1 nm by the Extreme ultraviolet Imaging Telescope instrument aboard the SOHO spacecraft

The Sun emits ultraviolet radiation in the UVA, UVB, and UVC bands, but because of absorption in the atmosphere's ozone layer, 99% of the ultraviolet radiation that reaches the Earth's surface is UVA. (Some of the UVC light is responsible for the generation of the ozone.) Download high resolution version (1024x1024, 809 KB)An image taken by the Solar and Heliospheric Observatory (SOHO) spacecrafts EIT instrument showing the corona in deep UV at 17. ... Download high resolution version (1024x1024, 809 KB)An image taken by the Solar and Heliospheric Observatory (SOHO) spacecrafts EIT instrument showing the corona in deep UV at 17. ... A Sun is the star at the centre of a solar system. ... The corona is the luminous atmosphere of the Sun extending millions of kilometres into space, most easily seen during a total solar eclipse, but also observable in a coronagraph. ... A nanometre (American spelling: nanometer) is 1. ... Categories: Stub ... The Solar and Heliospheric Observatory (SOHO) is a spacecraft launched in 1995 to study the sun. ... A Sun is the star at the centre of a solar system. ... Earths atmosphere is the layer of gases surrounding the planet Earth and retained by the Earths gravity. ... The ozone layer is that part of the Earths stratosphere which contains relatively high concentrations of ozone. ...


Ordinary glass is transparent to UVA but is opaque to shorter wavelengths. Silica or quartz glass, depending on quality, can be transparent even to vacuum UV wavelengths. Fused quartz is a man-made material manufactured principally from sands. ...


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 (less than about 10 ppm oxygen) 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 spectrometers, are also commonly nitrogen purged and operate in this spectral region. Circular dichroism, or CD, is defined as the differential absorption of left and right hand circularly polarized light. ...

Contents

Discovery

Soon after infrared 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, 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 (infrared), an illuminating component (visible light), and a reducing or hydrogenating component (ultraviolet). The unity of the different parts of the spectrum was not understood until about 1842, with the work of Macedonio Melloni, Alexandre-Edmond Becquerel and others. During that time, UV radiation was also called "actinic radiation". Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than visible light, but shorter than microwave radiation. ... Johann Wilhelm Ritter (1776 - 1810) was a German Chemist and Physicist. ... 1801 was a common year starting on Thursday (see link for calendar). ... Silver chloride (also called silver(I) chloride) is a chemical compound with chemical formula AgCl. ... Macedonio Melloni (April 11, 1798 – August 11, 1854) was an Italian physicist, notable for demonstrating that radiant heat has similar physical properties to those of light. ... Alexandre_Edmond Becquerel Alexandre_Edmond Becquerel (March 24, 1820 _ May 11, 1891) was a French physicist who studied the solar spectrum, magnetism, electricity, and optics. ...


Health effects

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

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. Because it does not cause reddening of the skin (erythema) it cannot be measured in the SPF testing. There is no good clinical measurement of the blocking of UVA radiation, but it is important that sunscreen block both UVA and UVB. Ultraviolet (UV) photons harm the DNA molecules of living organisms in different ways. ... Ultraviolet (UV) photons harm the DNA molecules of living organisms in different ways. ... Space-filling model of a section of DNA molecule Deoxyribose nucleic acid (DNA) is a nucleic acid that contains the genetic instructions specifying the biological development of all cellular forms of life (and many viruses). ...


High intensities of UVB light are hazardous to the eyes, and exposure can cause welder's flash (photokeratitis or arc eye). Arc eye is a painful condition sometimes experienced by welders who have failed to use adequate eye protection. ... Arc eye is a painful condition sometimes experienced by welders who have failed to use adequate eye protection. ...


UVA, UVB and UVC all can damage collagen fibers and thereby accelerate aging of the skin. Collagen is the main protein of connective tissue. ...


Tungsten-halogen lamps have bulbs made of quartz, not of ordinary glass. Tungsten-halogen lamps that are not filtered by an additional layer of ordinary glass are a common, useful, and possibly dangerous, source of UVB light. The incandescent light bulb uses a glowing wire filament heated to white-hot by electrical resistance, to generate light (a process known as thermal radiation). ...


UVA light is 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 wrinkles.


UVB light in particular has been linked to skin cancers such as melanoma. The radiation ionizes DNA molecules in skin cells, causing covalent bonds to form between adjacent 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 cancerous growths. The mutagenicity of UV radiation can be easily observed in bacteria cultures. In medicine (dermatology), there are several different types of cancer referred to under the general label of skin cancer. ... Skin cancer, close-up of level IV melanoma Melanoma is a malignant tumour of melanocytes . ... An ion is an elementary particle or system of elementary particles with a net electric charge. ... Space-filling model of a section of DNA molecule Deoxyribose nucleic acid (DNA) is a nucleic acid that contains the genetic instructions specifying the biological development of all cellular forms of life (and many viruses). ... Covalently bonded hydrogen and carbon in a molecule of methane. ... Thymine, also known as 5-methyluracil, is a pyrimidine nucleobase. ... This article is about mutation in biology, for other meanings see: mutation (disambiguation). ... When normal cells are damaged or old they undergo apoptosis; cancer cells, however, avoid apoptosis. ... In biology, a mutagen (Latin, literally origin of change) is an agent that changes the genetic information (usually DNA) of an organism and thus increases the number of mutations above the natural background level. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus_Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ...


This cancer connection is the reason for concern about ozone depletion and the ozone hole. Image of the largest antarctic ozone hole ever recorded in September 2000. ... Image of the largest antarctic ozone hole ever recorded in September 2000. ...


UVC rays are the strongest, most dangerous type of ultraviolet light. Little attention has been given to UVC rays in the past since they are normally filtered out by the ozone layer and do not reach the Earth. Thinning of the ozone layer and holes in the ozone layer are causing increased concern about the potential for UVC light exposure, however. The ozone layer is that part of the Earths stratosphere which contains relatively high concentrations of ozone. ... The ozone layer is that part of the Earths stratosphere which contains relatively high concentrations of ozone. ...


A positive effect of UV light is that it induces the production of vitamin D in the skin. Grant (2002) claims tens of thousands of premature deaths occur in the US annually from cancer due to insufficient UVB exposures (apparently via vitamin D deficiency). Another effect of vitamin D deficiency is osteomalacia, which can result in bone pain, difficulty in weight bearing and sometimes fractures. Vitamin D is a fat soluble vitamin that contributes to the maintenance of normal levels of calcium and phosphorus in the bloodstream. ...


Ultraviolet radiation has other medical applications, in the treatment of skin conditions such as psoriasis. UVB and UVA radiation can be used, in conjunction with psoralens (PUVA treatment). PUVA is a Psoralen + UVA treatment. ...


Protection

As a defense against UV radiation, the body tans when exposed to moderate (depending on skin type) levels of radiation by releasing the brown pigment melanin. 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 (often referred to as "sun block" or "sunscreen"). Most of these products contain an "SPF rating" that describes the amount of protection given. This protection applies only to UVB light. In any case, most dermatologists recommend against prolonged sunbathing. Historical data for native populations collected by R. Biasutti prior to 1940. ... Melanin is a pigment ranging from brown to black in hue found in animals and plants. ... Sunscreen or sunblock is a lotion that is applied to reduce skin damage by blocking ultraviolet radiation from the sun. ...


It is advisable to use protective eyewear when working with ultraviolet radiation, especially short wave ultraviolet. Ordinary eyeglasses give some protection. Most plastic lenses give more protection than glass lenses. Some plastic lens materials, such as polycarbonate, block most UV. There are protective treatments available for eyeglass lenses that need it to give better protection. The most important reason that ordinary eyeglasses only give limited protection, however, is that light can reach the eye without going through the lens. Full coverage is important if the risk from exposure is high. Full coverage eye protection is usually recommended for high altitude mountaineering, for instance. 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. Repeating chemical structure unit of Polycarbonate made from Bisphenol A Polycarbonates are a particular group of thermoplastics. ...


Uses

UV light has many various uses. Some of them are as follows:


Black lights

A black light is the name commonly given to a lamp emitting almost entirely long wave UV radiation and very little visible light. Ultraviolet radiation itself is invisible, but illuminating certain materials with UV radiation prompts the visible effects of fluorescence and phosphorescence. Black light testing is commonly used to authenticate antiques and bank notes. It is extensively used in non-destructive testing (NDT); fluorescing fluids are applied to metal structures and illuminated with a black light. Cracks and other artefacts can easily be detected. Black lights are used in forensic examination and testing, as naturally fluorescing remnants can be seen. Fluorescence induced by exposure to ultraviolet light in vials containing various sized cadmium selenide (CdSe) quantum dots. ... Phosphorescence is a radiative transition involving a change in the spin multiplicity of a molecule. ... Antique can stand for any of several things: An antique is an object, often furniture or any other domestic item, that is highly valued because of its age, or because it belongs to a specific time period. ... A £20 Ulster Bank banknote. ...


It is also used to illuminate pictures painted with fluorescent colors (preferably on black velvet to intensify the illusion of self-illumination). The fluorescence it prompts from certain textile fibers is also used as a recreational effect (as seen for instance in the opening credits of the James Bond film A View to a Kill). The black velvet is a cocktail made from Guinness Stout and a white, sparkling wine, traditionally Champagne. ... James Bond, also known as 007 (double-oh seven), is a sophisticated fictional character and British spy created by writer Ian Fleming. ... A View to a Kill, released in 1985, is the fourteenth entry in the James Bond series of films made by EON Productions, and the last to star Roger Moore as British Secret Service Agent, Commander James Bond. ...


Fluorescent lamps

Fluorescent lamps produce UV radiation by the emission of low-pressure mercury gas. A phosphorescent coating on the inside of the tubes absorbs the UV and becomes visible. A compact fluorescent lamp A fluorescent lamp is a type of electric lamp that excites argon and mercury vapor to create luminescence. ... General Name, Symbol, Number Mercury, Hg, 80 Chemical series transition metals Group, Period, Block 12 (IIB), 6, d Density, Hardness liquid 13. ...


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. U-shaped Xenon Flash Lamp A xenon flash lamp is a gas discharge lamp designed to produce extremely intense, incoherent, full-spectrum white light for very short durations. ...


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 is widely used as a technique in chemistry, for analysis of chemical structure, most notably conjugated systems. UV radiation is often used in visible spectrophotometry to determine the existence of fluorescence a given sample. Ultraviolet-Visible spectroscopy or Ultraviolet-Visible spectrophotometry (UV/VIS) involves the spectroscopy of photons (spectrophotometry). ... Chemistry (in Greek: χημεία) is the science of matter and its interactions with energy and itself (see physics, biology). ... Chemical structure is the arrangement of atoms within a molecule, usually linked by covalent bonds. ... A chemically conjugated system, is a system of atoms covalently bonded with alternating single and double bonds (e. ... In physics, spectrophotometry is the quantitative study of spectra. ...


Astronomy

In astronomy, very hot objects preferentially emit UV radiation (see Wien's law). However, the same ozone layer that protects us causes difficulties for astronomers observing from the Earth, so most UV observations are made from space. (see UV astronomy, space observatory) Astronomy (Greek: αστρονομία = άστρον + νόμος, literally, law of the stars) is the science involving the observation and explanation of events occurring beyond the Earth and its atmosphere. ... Wiens displacement law is a law of physics that states that there is an inverse relationship between the wavelength of the peak of the emission of a black body and its temperature. ... UV astronomy is the branch of astronomy and astrophysics which deals with objects visible in ultraviolet (UV) radiation. ... A space observatory is any object in outer space which is used for observation of distant planets, galaxies, and other outer space objects. ...


Analyzing minerals

Ultraviolet lamps are also used in analyzing minerals, 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. UV fluorescent dyes are used in many applications (for example, biochemistry and forensics). The fluorescent protein Green Fluorescent Protein (GFP) 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. Minerals are natural compounds formed through geological processes. ... A gemstone is a mineral, rock (as in lapis lazuli) or petrified material that when cut or faceted and polished is collectible or can be used in jewellery. ... A collectible (or collectable) is a manufactured item designed for people to collect. ... Fluorescence induced by exposure to ultraviolet light in vials containing various sized cadmium selenide (CdSe) quantum dots. ... A dye can generally be described as a coloured substance that has an affinity to the substrate to which it is being applied. ... Biochemistry is the chemistry of life. ... Forensics or forensic science is the application of science to questions which are of interest to the legal system as well as social sciences such as archaeology. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... The green fluorescent protein (GFP) is a protein from the jellyfish Aequorea victoria and the sea pansy that fluoresces green when exposed to blue light. ... Genetics (from the Greek genno γεννώ= give birth) is the science of genes, heredity, and the variation of organisms. ...


Photolithography

Ultraviolet radiation is used for very fine resolution photolithography, 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 step that either removes the exposed or unexposed photoresist), 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. Photolithography is a process used in semiconductor device fabrication to transfer a pattern from a photomask (also called reticle) to the surface of a wafer or substrate. ...


UV radiation is used extensively in the electronics industry because photolithography is used in the manufacture of semiconductors, integrated circuit components and printed circuit boards. A semiconductor is a material that is an insulator at very low temperature, but which has a sizable electrical conductivity at room temperature. ... An integrated circuit (IC) is a thin chip consisting of at least two interconnected semiconductor devices, mainly transistors, as well as passive components like resistors. ... Close-up photo of one side of a motherboard PCB, showing conductive traces, vias and solder points for through-hole components on the opposite side. ...


Checking electrical insulation

A new application of UV is to detect corona discharge (often simply called "corona") 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 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. [1] (http://www.seeing-corona.com/) In electricity, a corona discharge is an electrical discharge brought on by the ionization of a fluid surrounding a conductor, which occurs when the potential gradient exceeds a certain value, in situations where sparking is not favoured. ... Ozone (O3) is an allotrope of oxygen, the molecule consisting of three oxygen atoms instead of the more stable diatomic O2. ... Nitrogen has six different oxides: Nitric oxide (NO) Nitrous oxide (N2O) Nitrogen dioxide (NO2) Dinitrogen trioxide (N2O3) Dinitrogen tetroxide (N2O4) Dinitrogen pentoxide (N2O5) The term nitrogen oxide is imprecise and can be used to refer to any of these or to a mixture of them. ... Nitrous acid weak monobasic acid known only in solution and in the form of nitrite salts. ... The chemical compound nitric acid (HNO3), otherwise known as aqua fortis, is a colorless, corrosive liquid, a toxic acid which can cause severe burns. ...


Sterilization

Ultraviolet lamps are used to sterilize workspaces and tools used in biology laboratories and medical facilities. Conveniently, low pressure mercury discharge lamps emit about 50% of their light at the 253.7 nm mercury emission line which coincides very well with the peak of the germicidal effectiveness curve at 265 nm. UV light at this wavelength 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. 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. Sterility is the quality or state of being unable to reproduce. ... Thymine, also known as 5-methyluracil, is a pyrimidine nucleobase. ... Space-filling model of a section of DNA molecule Deoxyribose nucleic acid (DNA) is a nucleic acid that contains the genetic instructions specifying the biological development of all cellular forms of life (and many viruses). ... Sucrose, or common table sugar, is composed of glucose and fructose. ...


Disinfecting drinking water

Ultraviolet radiation is increasingly being used to disinfect drinking water and in waste water treatment plants. Recently it was discovered that ultraviolet radiation could treat Cryptosporidium, previously unknown. The findings resulted in two US patents (http://www.calgoncarbon.com/company/news/index.cfm?mode=detail&id=DF8B2807-AB22-705E-D9769AEA0B6A744E) and the use of UV radiation as a viable method to treat drinking water. Cryptosporidiosis is a disease affecting the intestines of mammals that is caused by Cryptosporidium, a protozoan parasite in the phylum Apicomplexa. ...


Fire detection

Ultraviolet (UV) detectors generally use either a solid-state device, such as one based on silicon carbide or aluminum nitride, 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 and artificial light. A burning hydrogen flame, for instance, radiates strongly in the 185 to 260 nanometre) range and only very weakly in the IR region, while a coal 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'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. Silicon carbide (SiC) or moissanite is a ceramic compound of silicon and carbon. ... Sunlight is also the trade name of the worlds first packaged, branded laundry soap producted by Lever Brothers. ... IR or ir may stand for: Information Retrieval Infrared international relations Iran (ISO country code) Iridium (Ir), chemical symbol for the chemical element Iran Air (IATA alpha code designator) investor relations Ingenieur (Ir) Irish Rail This is a disambiguation page — a navigational aid which lists other pages that might otherwise... Coal is a fossil fuel extracted from the ground either by underground mining, open-pit mining or strip mining. ... Radiation generally means the transmission of objects or information from a source into a surrounding medium or destination. ... A Sun is the star at the centre of a solar system. ... Earth, also known as the Earth or Terra, is the third planet outward from the Sun. ... Atmosphere may refer to: a celestial body atmosphere, e. ...


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 "see" a flame. Likewise, the presence of an oil mist in the air or an oil film on the detector window will have the same effect. In chemistry, a hydrocarbon is a group of chemical compounds consisting only of carbon (C) and hydrogen (H). ... In chemistry, a metal (Greek: Metallon) is an element that readily forms ions (cations) and has metallic bonds, and it is sometimes said that it is similar to a cation in a cloud of electrons. ... General Name, Symbol, Number sulfur, S, 16 Chemical series nonmetals Group, Period, Block 16 (VIA), 3, p Density, Hardness 1960 kg/m3, 2 Appearance Lemon yellow at STP Atomic properties Atomic weight 32. ... General Name, Symbol, Number Hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1 (IA), 1 , s Density, Hardness 0. ... Hydrazine is a chemical compound with formula N2H4 used as a rocket fuel. ... Ammonia is a chemical compound with the formula NH3. ... Manual Metal Arc welding, also known as stick or MMA welding is one of the most common forms of welding. ... Multiple cloud-to-ground and cloud-to-cloud lightning strokes are observed during a night-time thunderstorm. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz...


Curing of adhesives and coatings

Certain adhesives and coatings are formulated with photoinitiators. When exposed to the correct wavelengths 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, and the coating of flooring. An adhesive is a compound that adheres or bonds two items together. ...


See also

A UV index is a measuring of how strong the sun is. ...

References

  • Grant, William B. (2002). An estimate of premature cancer mortality in the US due to inadequate doses of solar ultraviolet-B radiation. (http://www3.interscience.wiley.com/cgi-bin/abstract/91016211/ABSTRACT) Cancer 94 (6), 1867–1875.
  • Matsumura Y, Ananthaswamy HN (2004). Toxic effects of UV radiation on the skin. (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15020192) Toxicol. Appl. Pharmacol. 195 (3), 298-308.
  • Hu S, et al. (2004). UV radiation and melanoma in US Hispanics & blacks. (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15262692) Arch Dermatol. 140 (7), 819-824.


Electromagnetic Spectrum

Radio waves | Microwave | Infrared | Optical spectrum | Ultraviolet | X-ray | Gamma ray
The electromagnetic spectrum encompasses all possible wavelengths of electromagnetic radiation. ... Radio frequency, or RF, refers to that portion of the electromagnetic spectrum in which electromagnetic waves can be generated by alternating current fed to an antenna. ... This page is about the radiation; for the appliance, see microwave oven. ... Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than visible light, but shorter than microwave radiation. ... The optical spectrum (light or visible spectrum) is the portion of the electromagnetic spectrum that is visible to the human eye. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... This article is about electromagnetic radiation. ...


Visible: Red | Orange | Yellow | Green | Blue | Indigo | Violet Red is a color at the lowest frequencies of light discernible by the human eye. ... The colour orange occurs between red and yellow in the visible spectrum at a wavelength of about 620-585 nanometres. ... Yellow is the color of light whose wavelength is between 565 nm and 590 nm, or is a mixture of red and green light that appears to be the same color. ... Green is a colour seen commonly in nature. ... Blue (from Old High German blao shining) is one of the three primary additive colors; blue light has the shortest wavelength range (about 420-490 nm) of the three primary colors. ... This article is about the color. ... Violet (named after the flower violet) refers to any of a group of reddish blue or bluish purple colors. ...


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