• Uv Krew Mask
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UV radiation is also produced. Must wear and cover their skin to prevent and serious.Ultraviolet ( UV) is with from 10 nm to 400 nm, shorter than that of but longer than. UV radiation is present in, and contributes about 10% of the total electromagnetic radiation output from the Sun.

It is also produced by and specialized lights, such as,. Although long-wavelength ultraviolet is not considered an because its lack the energy to, it can cause and causes many substances to glow. Consequently, the chemical and biological effects of UV are greater than simple heating effects, and many practical applications of UV radiation derive from its interactions with organic molecules.Short-wave ultraviolet light damages and sterilizes surfaces with which it comes into contact. For humans, and are familiar effects of exposure of the skin to UV light, along with an increased risks of. The amount of UV light produced by the Sun means that the Earth would not be able to sustain life on dry land if most of that light were not filtered out by the atmosphere. More energetic, shorter-wavelength 'extreme' UV below 121 nm ionizes air so strongly that it is absorbed before it reaches the ground.However, ultraviolet light is also responsible for the formation of bone-strengthening in most land vertebrates, including humans (specifically, UVB).

The UV spectrum thus has effects both beneficial and harmful to life.The lower wavelength limit of human vision is conventionally taken as 400 nm, so ultraviolet rays are invisible to humans, although some people can perceive light at slightly shorter wavelengths than this. Insects, birds, and some mammals can see near-UV (i.e. Slightly shorter wavelengths than humans can see). Contents.Visibility Ultraviolet rays are invisible to most humans. The blocks most radiation in the wavelength range of 300–400 nm; shorter wavelengths are blocked by the. Humans also lack color receptor adaptations for ultraviolet rays.

Nevertheless, the of the are sensitive to near-UV, and people lacking a lens (a condition known as ) perceive near-UV as whitish-blue or whitish-violet. Under some conditions, children and young adults can see ultraviolet down to wavelengths of about 310 nm. Near-UV radiation is visible to insects, some mammals,. Small birds have a fourth color receptor for ultraviolet rays; this gives birds 'true' UV vision. Discovery 'Ultraviolet' means 'beyond violet' (from ultra, 'beyond'), violet being the color of the highest frequencies of visible light. Ultraviolet has a higher frequency (and thus a shorter wavelength) than violet light.UV radiation was discovered in 1801 when the German physicist observed that invisible rays just beyond the violet end of the visible spectrum darkened -soaked paper more quickly than violet light itself.

He called them 'oxidizing rays' to emphasize and to distinguish them from 'heat rays', at the other end of the visible spectrum. The simpler term 'chemical rays' was adopted soon afterwards, and remained popular throughout the 19th century, although some said that this radiation was entirely different from light (notably, who named them 'tithonic rays' ). The terms 'chemical rays' and 'heat rays' were eventually dropped in favor of ultraviolet and, respectively.In 1878 the sterilizing effect of short-wavelength light by killing bacteria was discovered. By 1903 it was known the most effective wavelengths were around 250 nm. In 1960, the effect of ultraviolet radiation on DNA was established.The discovery of the ultraviolet radiation with wavelengths below 200 nm, named 'vacuum ultraviolet' because it is strongly absorbed by the oxygen in air, was made in 1893 by the German physicist. Levels of ozone at various altitudes and blocking of different bands of ultraviolet radiation.

In essence, all UVC is blocked by diatomic oxygen (100–200 nm) or by ozone (triatomic oxygen) (200–280 nm) in the atmosphere. The ozone layer then blocks most UVB. Meanwhile, UVA is hardly affected by ozone, and most of it reaches the ground. UVA makes up almost all UV light that penetrates the Earth's atmosphere.Some sources use the distinction of 'hard UV' and 'soft UV' - in the case of astrophysics the boundary may be at the i.e. Wavelength 91.2 nm, with 'hard UV' being more energetic.

The same terms may also used in other fields, such as, etc. the numerical value of the boundary between hard/soft even within similar scientific fields do not necessarily coincide; for example one applied physics publication used a boundary of 190 nm between hard and soft UV regions. Solar ultraviolet Very hot objects emit UV radiation (see ). The emits ultraviolet radiation at all wavelengths, including the extreme ultraviolet where it crosses into X-rays at 10 nm. Extremely hot emit proportionally more UV radiation than the Sun. In space at the top of Earth's atmosphere (see ) is composed of about 50% infrared light, 40% visible light, and 10% ultraviolet light, for a total intensity of about 1400 W/m 2 in vacuum.The atmosphere blocks about 77% of the Sun's UV, when the Sun is highest in the sky (at zenith), with absorption increasing at shorter UV wavelengths.

At ground level with the sun at zenith, sunlight is 44% visible light, 3% ultraviolet, and the remainder infrared. Of the ultraviolet radiation that reaches the Earth's surface, more than 95% is the longer wavelengths of UVA, with the small remainder UVB. There is essentially no UVC.

The fraction of UVB which remains in UV radiation after passing through the atmosphere is heavily dependent on cloud cover and atmospheric conditions. Thick clouds may block up to 90% of UVB radiation, but in 'partly cloudy' days, patches of blue sky showing between clouds are also sources of (scattered) UVA and UVB, which are produced by in the same way as the visible blue light from those parts of the sky. UV-B also plays a major role in plant development as it affects most of the plant hormones.The shorter bands of UVC, as well as even more-energetic UV radiation produced by the Sun, are absorbed by oxygen and generate the ozone in the when single oxygen atoms produced by UV of dioxygen react with more dioxygen. The ozone layer is especially important in blocking most UVB and the remaining part of UVC not already blocked by ordinary oxygen in air.Blockers and absorbers Ultraviolet absorbers are molecules used in organic materials (, etc.) to absorb UV radiation to reduce the (photo-oxidation) of a material. The absorbers can themselves degrade over time, so monitoring of absorber levels in weathered materials is necessary.In, ingredients that absorb UVA/UVB rays, such as, and, are or 'blockers'. They are contrasted with inorganic absorbers/'blockers' of UV radiation such as, and.For clothing, the (UPF) represents the ratio of -causing UV without and with the protection of the fabric, similar to SPF ratings for.

Standard summer fabrics have UPF of approximately 6, which means that about 20% of UV will pass through.Suspended nanoparticles in stained glass prevent UV rays from causing chemical reactions that change image colors. A set of stained glass color reference chips is planned to be used to calibrate the color cameras for the 2019 Mars rover mission, since they will remain unfaded by the high level of UV present at the surface of Mars.Common is partially to UVA but is to shorter wavelengths, whereas glass, depending on quality, can be transparent even to wavelengths.

Ordinary window glass passes about 90% of the light above 350 nm, but blocks over 90% of the light below 300 nm.is a nickel-bearing form of glass with a deep blue-purple color that blocks most visible light and passes ultraviolet.Artificial sources 'Black lights'. Main article:A black light lamp emits long-wave UVA radiation and little visible light.

Fluorescent black light lamps work similarly to other, but use a on the inner tube surface which emits UVA radiation instead of visible light. Some lamps use a deep-bluish-purple optical filter that blocks almost all visible light with wavelengths longer than 400 nanometres. Others use plain glass instead of the more expensive Wood's glass, so they appear light-blue to the eye when operating. Incandescent black lights are also produced, using a filter coating on the envelope of an incandescent bulb that absorbs visible light (see section below). These are cheaper but very inefficient, emitting only a fraction of a percent of their power as UV.

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Black lights in ratings up to 1 kW with UV-emitting phosphor and an envelope of Wood's glass are used for theatrical and concert displays. Black lights are used in applications in which extraneous visible light must be minimized; mainly to observe, the colored glow that many substances give off when exposed to UV light. UVA/UVB emitting bulbs are also sold for other special purposes, such as and reptile-keeping.Short-wave ultraviolet lamps. Commercial germicidal lamp in butcher shopShortwave UV lamps are made using a tube with no phosphor coating, composed of or, since ordinary glass absorbs UVC. These lamps emit ultraviolet light with two peaks in the UVC band at 253.7 nm and 185 nm due to the within the lamp, as well as some visible light.

From 85% to 90% of the UV produced by these lamps is at 253.7 nm, whereas only 5–10% is at 185 nm. The fused quartz tube passes the 253.7 nm radiation but blocks the 185 nm wavelength. Such tubes have two or three times the UVC power of a regular fluorescent lamp tube. These low-pressure lamps have a typical efficiency of approximately 30–40%, meaning that for every 100 watts of electricity consumed by the lamp, they will produce approximately 30–40 watts of total UV output. They also emit bluish-white visible light, due to mercury's other spectral lines.

These 'germicidal' lamps are used extensively for disinfection of surfaces in laboratories and food-processing industries, and for disinfecting water supplies.Incandescent lamps 'Black light' are also made, from an incandescent light bulb with a filter coating which absorbs most visible light. With envelopes are used as inexpensive UV light sources in the near UV range, from 400 to 300 nm, in some scientific instruments. Due to its a filament light bulb is a very inefficient ultraviolet source, emitting only a fraction of a percent of its energy as UV.Gas-discharge lamps. Main article:Specialized UV gas-discharge lamps containing different gases produce UV radiation at particular spectral lines for scientific purposes. And are often used as stable sources, either windowless or with various windows such as. These are often the emitting sources in UV spectroscopy equipment for chemical analysis.Other UV sources with more continuous emission spectra include (commonly used as sunlight simulators), and.The, a UV source developed in the early 2000s, is seeing increasing use in scientific fields. It has the advantages of high-intensity, high efficiency, and operation at a variety of wavelength bands into the vacuum ultraviolet.Ultraviolet LEDs.

A 380 nanometre UV LED makes some common household items fluoresce.(LEDs) can be manufactured to emit radiation in the ultraviolet range. In 2019, following significant advances over the preceding five years, UVA LEDs of 365 nm and longer wavelength were available with efficiencies of 50 percent at 1000 mW output. Such LEDs are increasingly used for applications, and are already successful in digital print applications and inert UV curing environments. Power densities approaching 3 W/cm 2 (30 kW/m 2) are now possible, and this, coupled with recent developments by photoinitiator and resin formulators, makes the expansion of LED-cured UV materials likely.UVC LEDs are beginning to be used in disinfection and as line sources to replace in instruments. Ultraviolet lasers. Main article:, and can be manufactured to emit ultraviolet rays, and lasers are available which cover the entire UV range. The uses electronic excitation of nitrogen molecules to emit a beam that is mostly UV.

The strongest ultraviolet lines are at 337.1 nm and 357.6.6 nm, wavelength. Another type of high power gas laser is the. They are widely used lasers emitting in ultraviolet and vacuum ultraviolet wavelength ranges. Presently, UV (ArF) excimer lasers operating at 193 nm are routinely used in production. The current wavelength limit of production of coherent UV is about 126 nm, characteristic of the Ar 2. excimer laser.Direct UV-emitting laser diodes are available at 375 nm. UV diode-pumped solid state lasers have been demonstrated using Ce:LiSAF crystals (- lithium strontium aluminum fluoride), a process developed in the 1990s at.

Wavelengths shorter than 325 nm are commercially generated in. Ultraviolet lasers can also be made by applying to lower-frequency lasers.Ultraviolet have applications in industry , medicine (, and ), chemistry , computing and manufacture of integrated circuits.Tunable vacuum ultraviolet (VUV) via sum and difference frequency mixing The vacuum ultraviolet (VUV) band (100–200 nm) can be generated by in gases by sum or difference frequency mixing of 2 or more longer wavelength lasers.

The generation is generally done in gasses (e.g. Krypton, hydrogen which are two-photon resonant near 193 nm) or metal vapors (e.g. By making one of the lasers tunable, the VUV can be tuned. If one of the lasers is resonant with a transition in the gas or vapor then the VUV production is intensified. However, resonances also generate wavelength dispersion, and thus the phase matching can limit the tunable range of the 4 wave mixing.

Difference frequency mixing (lambda1 + lambda2 − lambda3) has an advantage over sum frequency mixing because the phase matching can provide greater tuning. In particular, difference frequency mixing two photons of an ArF (193 nm) excimer laser with a tunable visible or near IR laser in hydrogen or krypton provides resonantly enhanced tunable VUV covering from 100 nm to 200 nm. Practically, the lack of suitable gas/vapor cell window materials above the lithium fluoride cut-off wavelength limit the tuning range to longer than about 110 nm. Tunable VUV wavelengths down to 75 nm was achieved using window-free configurations. Plasma and synchrotron sources of extreme UV Lasers have been used to indirectly generate non-coherent extreme UV (EUV) radiation at 13.5 nm for. The EUV is not emitted by the laser, but rather by electron transitions in an extremely hot tin or xenon plasma, which is excited by an excimer laser. This technique does not require a synchrotron, yet can produce UV at the edge of the X-ray spectrum.

Can also produce all wavelengths of UV, including those at the boundary of the UV and X-ray spectra at 10 nm.Human health-related effects. Further information:The impact of ultraviolet radiation on has implications for the risks and benefits of sun exposure and is also implicated in issues such as. Getting too much sun exposure can be harmful, but in moderation, sun exposure is beneficial. Beneficial effects There is no doubt that a little sunlight is good for you! But 5 to 15 minutes of casual sun exposure of hands, face and arms two to three times a week during the summer months is sufficient to keep your vitamin D levels high.— World Health OrganizationUV light causes the body to produce (specifically, UVB), which is essential for life.

The human body needs some UV radiation in order for one to maintain adequate vitamin D levels; however, excess exposure produces harmful effects that typically outweigh the benefits.Vitamin D promotes the creation of. The production of serotonin is in direct proportion to the degree of bright sunlight the body receives. Serotonin is thought to provide sensations of happiness, well being and serenity to human beings. Skin conditions UV rays also treat certain skin conditions. Modern phototherapy has been used to successfully treat psoriasis, eczema, jaundice, vitiligo, atopic dermatitis, and localized scleroderma. In addition, UV light, in particular UVB radiation, has been shown to induce arrest in keratinocytes, the most common type of skin cell.

As such, sunlight therapy can be a candidate for treatment of conditions such as and, conditions in which skin cells divide more rapidly than usual or necessary. Harmful effects In humans, excessive exposure to UV radiation can result in acute and chronic harmful effects on the eye's dioptric system and retina.

The risk is elevated at high altitudes and people living in high latitude countries where snow covers the ground right into early summer and sun positions even at zenith are low, are particularly at risk. Skin, the and can also be affected. Sunburn effect (as measured by the ) is the product of the sunlight spectrum (radiation intensity) and the erythemal action spectrum (skin sensitivity) across the range of UV wavelengths. Sunburn production per milliwatt is increased by almost a factor of 100 between the near UVB wavelengths of 315–295 nmThe differential effects of various wavelengths of light on the human cornea and skin are sometimes called the 'erythemal action spectrum'. The action spectrum shows that UVA does not cause immediate reaction, but rather UV begins to cause photokeratitis and skin redness (with Caucasians more sensitive) at wavelengths starting near the beginning of the UVB band at 315 nm, and rapidly increasing to 300 nm. The skin and eyes are most sensitive to damage by UV at 265–275 nm, which is in the lower UVC band.

At still shorter wavelengths of UV, damage continues to happen, but the overt effects are not as great with so little penetrating the atmosphere. The WHO-standard is a widely publicized measurement of total strength of UV wavelengths that cause sunburn on human skin, by weighting UV exposure for action spectrum effects at a given time and location. This standard shows that most sunburn happens due to UV at wavelengths near the boundary of the UVA and UVB bands.Skin damage Overexposure to UVB radiation not only can cause but also some forms of.

However, the degree of redness and eye irritation (which are largely not caused by UVA) do not predict the long-term effects of UV, although they do mirror the direct damage of DNA by ultraviolet.All bands of UV radiation damage fibers and accelerate aging of the skin. Both UVA and UVB destroy vitamin A in skin, which may cause further damage.UVB radiation can cause direct DNA damage. This cancer connection is one reason for concern about and the ozone hole.The most deadly form of, malignant, is mostly caused by DNA damage independent from UVA radiation. This can be seen from the absence of a direct UV signature mutation in 92% of all melanoma. Occasional overexposure and sunburn are probably greater risk factors for melanoma than long-term moderate exposure. UVC is the highest-energy, most-dangerous type of ultraviolet radiation, and causes adverse effects that can variously be mutagenic or carcinogenic.In the past, UVA was considered not harmful or less harmful than UVB, but today it is known to contribute to skin cancer via (free radicals such as reactive oxygen species).

UVA can generate highly reactive chemical intermediates, such as hydroxyl and oxygen radicals, which in turn can damage DNA. The DNA damage caused indirectly to skin by UVA consists mostly of single-strand breaks in DNA, while the damage caused by UVB includes direct formation of or and double-strand DNA breakage. UVA is immunosuppressive for the entire body (accounting for a large part of the immunosuppressive effects of sunlight exposure), and is mutagenic for basal cell keratinocytes in skin.UVB photons can cause direct DNA damage.

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UVB radiation DNA molecules in skin cells, causing aberrant to form between adjacent bases, producing a. Most UV-induced pyrimidine dimers in DNA are removed by the process known as that employs about 30 different proteins. Those pyrimidine dimers that escape this repair process can induce a form of programmed cell death or can cause DNA replication errors leading to.As a defense against UV radiation, the amount of the brown pigment in the skin increases when exposed to moderate (depending on ) levels of radiation; this is commonly known as a. The purpose of melanin is to absorb UV radiation and dissipate the energy as harmless heat, protecting the skin against both and from the UV. UVA gives a quick tan that lasts for days by oxidizing melanin that was already present and triggers the release of the from melanocytes. UVB yields a tan that takes roughly 2 days to develop because it stimulates the body to produce more melanin.Sunscreen safety debate. Demonstration of the effect of sunscreen.

The man's face has sunscreen on his right only. The left image is a regular photograph of the face; the right image is taken by reflected UV light. The side of the face with sunscreen is darker because the sunscreen absorbs the UV light.Medical organizations recommend that patients protect themselves from UV radiation by using. Five sunscreen ingredients have been shown to protect mice against skin tumors. However, produce potentially harmful substances if they are illuminated while in contact with living cells. The amount of sunscreen that penetrates into the lower layers of the skin may be large enough to cause damage.Sunscreen reduces the direct DNA damage that causes sunburn, by blocking UVB, and the usual indicates how effectively this radiation is blocked. SPF is, therefore, also called UVB-PF, for 'UVB protection factor'.

This rating, however, offers no data about important protection against UVA, which does not primarily cause sunburn but is still harmful, since it causes indirect DNA damage and is also considered carcinogenic. Several studies suggest that the absence of UVA filters may be the cause of the higher incidence of melanoma found in sunscreen users compared to non-users. Some sunscreen lotions now contain compounds including, and which helps protect against UVA rays.The photochemical properties of melanin make it an excellent.

However, sunscreen chemicals cannot dissipate the energy of the excited state as efficiently as melanin and therefore, if sunscreen ingredients penetrate into the lower layers of the skin, the amount of may be increased. The amount of sunscreen that penetrates through the may or may not be large enough to cause damage.In an experiment by Hanson et al. That was published in 2006, the amount of harmful (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 number of ROS species was smaller. After 60 minutes, however, the amount of absorbed sunscreen was so high that the amount of ROS was higher in the sunscreen-treated skin than in the untreated skin.

The study indicates that sunscreen must be reapplied within 2 hours in order to prevent UV light from penetrating to sunscreen-infused live skin cells. Aggravation of certain skin conditions Ultraviolet radiation can aggravate several skin conditions and diseases, including, and.Eye damage. Signs are often used to warn of the hazard of strong UV sources.The eye is most sensitive to damage by UV in the lower UVC band at 265–275 nm. Radiation of this wavelength is almost absent from sunlight but is found in welder's arc lights and other artificial sources.

Exposure to these can cause 'welder's flash' or 'arc eye' and can lead to, and formation. To a lesser extent, UVB in sunlight from 310–280 nm also causes photokeratitis ('snow blindness'), and the, the, and the can be damaged.is beneficial to those exposed to ultraviolet radiation.

Since light can reach the eyes 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 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, inherently block most UV.

Degradation of polymers, pigments and dyes. UV damaged rope (left) and new rope (right)is one form of that affects plastics exposed to. The problem appears as discoloration or fading, cracking, loss of strength or disintegration. The effects of attack increase with exposure time and sunlight intensity. The addition of UV absorbers inhibits the effect.Sensitive polymers include and speciality fibers like.

UV absorption leads to chain degradation and loss of strength at sensitive points in the chain structure. Aramid rope must be shielded with a sheath of thermoplastic if it is to retain its strength. IR spectrum showing carbonyl absorption due to UV degradation ofMany and absorb UV and change colour, so and textiles may need extra protection both from sunlight and fluorescent bulbs, two common sources of UV radiation. Window glass absorbs some harmful UV, but valuable artifacts need extra shielding.

Many museums place black curtains over and ancient textiles, for example. Since watercolours can have very low pigment levels, they need extra protection from UV.

Various forms of, including acrylics (plexiglass), laminates, and coatings, offer different degrees of UV (and visible light) protection.Applications Because of its ability to cause chemical reactions and excite in materials, ultraviolet radiation has a number of applications. The following table gives some uses of specific wavelength bands in the UV spectrum. 13.5 nm:. 30–200 nm:, standard manufacture by. 230–365 nm: UV-ID, label tracking,. 230–400 nm: Optical, various instrumentation. 240–280 nm:, decontamination of surfaces and water ( absorption has a peak at 260 nm).

200–400 nm:, drug detection. 270–360 nm: analysis,. 280–400 nm: of. 300–320 nm: in medicine.

300–365 nm: of and. 350–370 nm: (flies are most attracted to light at 365 nm)Photography. A portrait taken using only UV light between the wavelengths of 335 and 365 nanometers.Photographic film responds to ultraviolet radiation but the glass lenses of cameras usually block radiation shorter than 350 nm. Slightly yellow UV-blocking filters are often used for outdoor photography to prevent unwanted bluing and overexposure by UV rays. For photography in the near UV, special filters may be used. Photography with wavelengths shorter than 350 nm requires special quartz lenses which do not absorb the radiation.Digital cameras sensors may have internal filters that block UV to improve color rendition accuracy. Sometimes these internal filters can be removed, or they may be absent, and an external visible-light filter prepares the camera for near-UV photography.

A few cameras are designed for use in the UV.Photography by reflected ultraviolet radiation is useful for medical, scientific, and forensic investigations, in applications as widespread as detecting bruising of skin, alterations of documents, or restoration work on paintings. Photography of the fluorescence produced by ultraviolet illumination uses visible wavelengths of light. Aurora at 's north pole as seen in ultraviolet light by the.In, measurements are used to discern the chemical composition of the interstellar medium, and the temperature and composition of stars. Because the ozone layer blocks many UV frequencies from reaching telescopes on the surface of the Earth, most UV observations are made from space.Electrical and electronics industry on electrical apparatus can be detected by its ultraviolet emissions. Corona causes degradation of electrical insulation and emission of and.(Erasable Programmable Read-Only Memory) are erased by exposure to UV radiation.

These modules have a transparent window on the top of the chip that allows the UV radiation in.Fluorescent dye uses Colorless fluorescent dyes that emit blue light under UV are added as to paper and fabrics. The blue light emitted by these agents counteracts yellow tints that may be present and causes the colors and whites to appear whiter or more brightly colored.UV fluorescent dyes that glow in the primary colors are used in paints, papers, and textiles either to enhance color under daylight illumination or to provide special effects when lit with UV lamps. That contain dyes that glow under UV are used in a number of art and aesthetic applications.Amusement parks often use UV lighting to fluoresce ride artwork and backdrops. This often has the side effect of causing rider's white clothing to glow light-purple. A bird appears on many Visa credit cards when they are held under a UV light sourceTo help prevent of currency, or forgery of important documents such as driver's licenses and, the paper may include a UV or fluorescent multicolor fibers that are visible under ultraviolet light. Postage stamps are with a phosphor that glows under UV rays to permit automatic detection of the stamp and facing of the letter.UV fluorescent are used in many applications (for example, and ).

Some brands of will leave an invisible chemical (UV dye) that is not easily washed off on a pepper-sprayed attacker, which would help police identify the attacker later.In some types of UV stimulates fluorescent dyes to highlight defects in a broad range of materials. These dyes may be carried into surface-breaking defects by capillary action or they may be bound to ferrite particles caught in magnetic leakage fields in ferrous materials.Analytic uses Forensics UV is an investigative tool at the crime scene helpful in locating and identifying bodily fluids such as semen, blood, and saliva.

For example, ejaculated fluids or saliva can be detected by high-power UV sources, irrespective of the structure or colour of the surface the fluid is deposited upon.is also used to analyze trace evidence, such as textile fibers and paint chips, as well as questioned documents.Other applications include the authentication of various collectibles and art, and detecting counterfeit currency. Even materials not specially marked with UV sensitive dyes may have distinctive fluorescence under UV exposure or may fluoresce differently under short-wave versus long-wave ultraviolet.Enhancing contrast of ink Using multi-spectral imaging it is possible to read illegible, such as the burned papyri of the or of, or the. The technique involves taking pictures of the illegible document 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 on vellum. Sanitary compliance. After a training exercise involving fake, a healthcare worker's is checked with ultraviolet light to find invisible drops of fluids. These fluids could contain deadly viruses or other contamination.Ultraviolet aids in the detection of organic material deposits that remain on surfaces where periodic cleaning and sanitizing may not have been properly accomplished. It is used in the hotel industry, manufacturing, and other industries where levels of cleanliness or contamination are.Perennial news features for many television news organizations involve an investigative reporter using a similar device to reveal unsanitary conditions in hotels, public toilets, hand rails, and such.

Chemistry is widely used as a technique in to analyze, the most notable one being. UV radiation is often used to excite a given sample where the fluorescent emission is measured with a. In biological research, UV radiation is used for. 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 and.In pollution control applications, ultraviolet analyzers are used to detect emissions of nitrogen oxides, sulfur compounds, mercury, and ammonia, for example in the flue gas of fossil-fired power plants. Ultraviolet radiation can detect thin sheens of on water, either by the high reflectivity of oil films at UV wavelengths, fluorescence of compounds in oil or by absorbing of UV created by in water. Material science uses Fire detection.

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See also:In general, ultraviolet detectors use either a solid-state device, such as one based on or, or a gas-filled tube as the sensing element. UV detectors that are sensitive to UV in any part of the spectrum respond to irradiation. A burning hydrogen flame, for instance, radiates strongly in the 185- to 260-nanometer range and only very weakly in the 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 in the UVC band, whereas the 's radiation at this band is absorbed by the. 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, metals, and., electrical arcs, 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.Photolithography Ultraviolet radiation is used for very fine resolution, a procedure wherein a chemical called a photoresist is exposed to UV radiation that has passed through a mask. The exposure causes chemical reactions to occur in the photoresist. After removal of unwanted photoresist, a pattern determined by the mask remains on the sample.

Steps may then be taken to 'etch' away, deposit on or otherwise modify areas of the sample where no photoresist remains.Photolithography is used in the manufacture of, components,. Photolithography processes used to fabricate electronic integrated circuits presently use 193 nm UV and are experimentally using 13.5 nm UV for.Polymers Electronic components that require clear transparency for light to exit or enter (photovoltaic panels and sensors) can be potted using acrylic resins that are cured using UV energy. The advantages are low VOC emissions and rapid curing. Effects of UV on finished surfaces in 0, 20 and 43 hours.Certain inks, coatings, and are formulated with photoinitiators and resins. When exposed to UV light, occurs, and so the adhesives harden or cure, usually within a few seconds. Applications include glass and plastic bonding, coatings, the coating of flooring, and paper finishes in offset, dental fillings, and decorative fingernail 'gels'.UV sources for UV curing applications include, UV, and flash lamps.

Fast processes such as flexo or offset printing require high-intensity light focused via reflectors onto a moving substrate and medium so high-pressure (mercury) or (iron, doped)-based bulbs are used, energized with electric arcs or microwaves. Lower-power fluorescent lamps and LEDs can be used for static applications.

Small high-pressure lamps can have light focused and transmitted to the work area via liquid-filled or fiber-optic light guides.The impact of UV on polymers is used for modification of the ( and ) of polymer surfaces. For example, a surface can be smoothed by vacuum ultraviolet.UV radiation is useful in preparing low-surface-energy for adhesives. Polymers exposed to UV will oxidize, thus raising the of the polymer.

Once the surface energy of the polymer has been raised, the bond between the adhesive and the polymer is stronger.Biology-related uses Air purification Using a from and UVC exposure, of organic matter converts, and into harmless inert byproducts. However, the reaction of titanium dioxide and UVC is not a straight path. Several hundreds of reactions occur prior to the inert byproducts stage and can hinder the resulting reaction creating formadehyde, aldehyde, and other VOC's en route to a final stage.

Thus, the use of Titanium Dioxide and UVC requires very specific parameters for a successful outcome. The cleansing mechanism of UV is a photochemical process. Contaminants in the indoor environment are almost entirely organic carbon-based compounds, which break down when exposed to high-intensity UV at 240 to 280 nm. Short-wave ultraviolet radiation can destroy DNA in living microorganisms. UVC's effectiveness is directly related to intensity and exposure time.UV has also been shown to reduce gaseous contaminants such as.

UV lamps radiating at 184 and 254 nm can remove low concentrations of and if the air is recycled between the room and the lamp chamber. This arrangement prevents the introduction of ozone into the treated air. Likewise, air may be treated by passing by a single UV source operating at 184 nm and passed over iron pentaoxide to remove the ozone produced by the UV lamp.Sterilization and disinfection.

A low-pressure mercury vapor discharge tube floods the inside of a with shortwave UV light when not in use, microbiological contaminants from irradiated surfaces.are used to workspaces and tools used in biology laboratories and medical facilities. Commercially available low-pressure emit about 86% of their radiation at 254 nanometers (nm), with 265 nm being the peak germicidal effectiveness curve. UV at these germicidal wavelengths damage a microorganism's DNA so that it cannot reproduce, making it harmless, (even though the organism may not be killed). Since microorganisms can be shielded from ultraviolet rays in small cracks and other shaded areas, these lamps are used only as a supplement to other sterilization techniques.UV-C LEDs are relatively new to the commercial market and are gaining in popularity. Due to their monochromatic nature (± 5 nm) these LEDs can target a specific wavelength needed for disinfection.

This is especially important knowing that pathogens vary in their sensitivity to specific UV wavelengths. LEDs are mercury free, instant on/off, and have unlimited cycling throughout the day.using UV radiation is commonly used in treatment applications and is finding an increased usage in municipal drinking. Many bottlers of spring water use UV disinfection equipment to sterilize their water. Has been researched for cheaply treating contaminated water using natural. The UV-A irradiation and increased water temperature kill organisms in the water.Ultraviolet radiation is used in several food processes to kill unwanted. UV can be used to fruit juices by flowing the juice over a high-intensity ultraviolet source.

The effectiveness of such a process depends on the UV of the juice.(PL) is a technique of killing microorganisms on surfaces using pulses of an intense broad spectrum, rich in UV-C between 200 and 280. Pulsed light works with that can produce flashes several times per second.

Use pulsed UV Biological Some animals, including birds, reptiles, and insects such as bees, can see near-ultraviolet wavelengths. 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, are 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 for sex recognition and mating behavior.

For example, in the butterfly, males rely on visual cues to locate and identify females. Instead of using chemical stimuli to find mates, males are attracted to the ultraviolet-reflecting color of female hind wings. In butterflies it was shown that females in northern Finland with less UV-radiation present in the environment possessed stronger UV signals to attract their males than those occurring further south. This suggested that it was evolutionarily more difficult to increase the UV-sensitivity of the eyes of the males than to increase the UV-signals emitted by the females.Many insects use the ultraviolet wavelength emissions from celestial objects as references for flight navigation. A local ultraviolet emitter will normally disrupt the navigation process and will eventually attract the flying insect. Entomologist using a UV light for collecting in,.The (GFP) is often used in as a marker. Many substances, such as proteins, have significant light absorption bands in the ultraviolet that are of interest in biochemistry and related fields.

UV-capable spectrophotometers are common in such laboratories.Ultraviolet traps called are used to eliminate various small flying insects. They are attracted to the UV and are killed using an electric shock, or trapped once they come into contact with the device. Different designs of ultraviolet radiation traps are also used by for insects during survey studies.Therapy. Main article:Ultraviolet radiation is helpful in the treatment of such as.

Exposure to UVA, while the skin is hyper-photosensitive, by taking is an effective treatment for. Due to the potential of to cause damage to the, may be used only a limited number of times over a patient's lifetime.UVB phototherapy does not require additional medications or topical preparations for the therapeutic benefit; only the 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. Herpetology need UVB for biosynthesis of vitamin D, and other metabolic processes. Specifically (vitamin D3), which is needed to for basic cellular / neural functioning as well as the utilization calcium for bone and egg production. The UVA wavelength is also visible to many reptiles and might play a significant role in their ability survive in the wild as well as visual communication between individuals.

Therefore, in a typical reptile enclosure, a fluorescent UV a/b source (at the proper strength / spectrum for the species), must be available for many captive species to survive. Simple supplementation with (Vitamin D3) will not be enough as there's a complete biosynthetic pathway that is 'leapfrogged' (risks of possible overdoses), the intermediate molecules and metabolites also place important functions in the animals health. Natural sunlight in the right levels is always going to be superior to artificial sources, but this might be possible for keepers in different parts of the world.It is a known problem that high levels of output of the UVa part of the spectrum can both cause cellular and DNA damage to sensitive parts of their bodies - especially the eyes were blindness is the result from an improper UVa/b source use and placement.

For many keepers there must also be a provision for an adequate heat source this has resulted in the marketing of heat and light 'combination' products. Keepers should be careful of these 'combination' light/ heat and UVa/b generators, they typically emit high levels of UVa with lower levels of UVb that are set and difficult to control so that animals can have their needs met. A better strategy is to use individual sources of these elements and so they can be placed and controlled by the keepers for the max benefit of the animals. Evolutionary significance The evolution of early reproductive and is attributed in modern models of to ultraviolet radiation. UVB causes base pairs next to each other in genetic sequences to bond together into, a disruption in the strand that reproductive enzymes cannot copy.

This leads to during genetic replication and, usually killing the cell. Before formation of the UV-blocking ozone layer, when early prokaryotes approached the surface of the ocean, they almost invariably died out. The few that survived had developed enzymes that monitored the genetic material and removed by enzymes. Many enzymes and proteins involved in modern and are similar to repair enzymes, and are believed to be evolved modifications of the enzymes originally used to overcome DNA damages caused by UV. See also.References.

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