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82-511: VUV may stand for: Vacuum UV , ultraviolet radiation that is absorbed by air Vanuatu vatu (ISO 4217: VUV), the official currency of Vanuatu A nickname for the Vuvuzela horn, commonly used in soccer games Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title VUV . If an internal link led you here, you may wish to change

164-492: A band in the vicinity of 400–790  terahertz . These boundaries are not sharply defined and may vary per individual. Under optimal conditions, these limits of human perception can extend to 310 nm (ultraviolet) and 1100 nm (near infrared). The spectrum does not contain all the colors that the human visual system can distinguish. Unsaturated colors such as pink , or purple variations like magenta , for example, are absent because they can only be made from

246-486: A boundary of 190 nm between hard and soft UV regions. Very hot objects emit UV radiation (see black-body radiation ). The Sun emits ultraviolet radiation at all wavelengths, including the extreme ultraviolet where it crosses into X-rays at 10 nm. Extremely hot stars (such as O- and B-type) emit proportionally more UV radiation than the Sun. Sunlight in space at the top of Earth's atmosphere (see solar constant )

328-433: A deep-bluish-purple Wood's glass optical filter that blocks almost all visible light with wavelengths longer than 400 nanometers. The purple glow given off by these tubes is not the ultraviolet itself, but visible purple light from mercury's 404 nm spectral line which escapes being filtered out by the coating. Other black lights use plain glass instead of the more expensive Wood's glass, so they appear light-blue to

410-671: A filter coating which absorbs most visible light. Halogen lamps with fused quartz 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 black-body spectrum a filament light bulb is a very inefficient ultraviolet source, emitting only a fraction of a percent of its energy as UV. Specialized UV gas-discharge lamps containing different gases produce UV radiation at particular spectral lines for scientific purposes. Argon and deuterium arc lamps are often used as stable sources, either windowless or with various windows such as magnesium fluoride . These are often

492-486: A ghostly optical afterimage , as did Schopenhauer in On Vision and Colors . Goethe argued that the continuous spectrum was a compound phenomenon. Where Newton narrowed the beam of light to isolate the phenomenon, Goethe observed that a wider aperture produces not a spectrum but rather reddish-yellow and blue-cyan edges with white between them. The spectrum appears only when these edges are close enough to overlap. In

574-652: 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. Overexposure to UVB radiation not only can cause sunburn but also some forms of skin cancer . 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. Visible spectrum A typical human eye will respond to wavelengths from about 380 to about 750 nanometers . In terms of frequency, this corresponds to

656-449: A hard cutoff, but rather an exponential decay, such that the function's value (or vision sensitivity) at 1,050 nm is about 10 times weaker than at 700 nm; much higher intensity is therefore required to perceive 1,050 nm light than 700 nm light. Under ideal laboratory conditions, subjects may perceive infrared light up to at least 1,064 nm. While 1,050 nm NIR light can evoke red, suggesting direct absorption by

738-459: A mix of multiple wavelengths. Colors containing only one wavelength are also called pure colors or spectral colors . Visible wavelengths pass largely unattenuated through the Earth's atmosphere via the " optical window " region of the electromagnetic spectrum. An example of this phenomenon is when clean air scatters blue light more than red light, and so the midday sky appears blue (apart from

820-404: A narrow band of wavelengths ( monochromatic light ) are called pure spectral colors . The various color ranges indicated in the illustration are an approximation: The spectrum is continuous, with no clear boundaries between one color and the next. In the 13th century, Roger Bacon theorized that rainbows were produced by a similar process to the passage of light through glass or crystal. In

902-551: A number of ranges recommended by the ISO standard ISO 21348: Several solid-state and vacuum devices have been explored for use in different parts of the UV spectrum. Many approaches seek to adapt visible light-sensing devices, but these can suffer from unwanted response to visible light and various instabilities. Ultraviolet can be detected by suitable photodiodes and photocathodes , which can be tailored to be sensitive to different parts of

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984-485: A slightly more truncated red vision. Most other vertebrates (birds, lizards, fish, etc.) have retained their tetrachromacy , including UVS opsins that extend further into the ultraviolet than humans' VS opsin. The sensitivity of avian UVS opsins vary greatly, from 355–425 nm, and LWS opsins from 560–570 nm. This translates to some birds with a visible spectrum on par with humans, and other birds with greatly expanded sensitivity to UV light. The LWS opsin of birds

1066-520: 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. 'Black light' incandescent lamps are also made from an incandescent light bulb with

1148-449: A variety of wavelength bands into the vacuum ultraviolet. Light-emitting diodes (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% at 1.0 W output. Currently, the most common types of UV LEDs are in 395 nm and 365 nm wavelengths, both of which are in

1230-560: Is electromagnetic radiation of wavelengths of 10–400 nanometers , shorter than that of visible light , but longer than X-rays . UV radiation is present in sunlight , and constitutes about 10% of the total electromagnetic radiation output from the Sun. It is also produced by electric arcs , Cherenkov radiation , and specialized lights, such as mercury-vapor lamps , tanning lamps , and black lights . The photons of ultraviolet have greater energy than those of visible light, from about 3.1 to 12  electron volts , around

1312-473: Is ionizing radiation . Consequently, short-wave UV damages DNA and sterilizes surfaces with which it comes into contact. For humans, suntan and sunburn are familiar effects of exposure of the skin to UV, along with an increased risk of skin cancer . The amount of UV radiation 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

1394-430: Is reflected and some of the beam passes into and through the glass, emerging as different-colored bands. Newton hypothesized light to be made up of "corpuscles" (particles) of different colors, with the different colors of light moving at different speeds in transparent matter, red light moving more quickly than violet in glass. The result is that red light is bent ( refracted ) less sharply than violet as it passes through

1476-1051: 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 cerium - doped lithium strontium aluminum fluoride crystals (Ce:LiSAF), a process developed in the 1990s at Lawrence Livermore National Laboratory . Wavelengths shorter than 325 nm are commercially generated in diode-pumped solid-state lasers . Ultraviolet lasers can also be made by applying frequency conversion to lower-frequency lasers. Ultraviolet lasers have applications in industry ( laser engraving ), medicine ( dermatology , and keratectomy ), chemistry ( MALDI ), free-air secure communications , computing ( optical storage ), and manufacture of integrated circuits. The vacuum ultraviolet (V‑UV) band (100–200 nm) can be generated by non-linear 4 wave mixing in gases by sum or difference frequency mixing of 2 or more longer wavelength lasers. The generation

1558-404: Is absorbed by the ocular media (lens and cornea), it may fluoresce and be released at a lower energy (longer wavelength) that can then be absorbed by the opsins. For example, when the lens absorbs 350 nm light, the fluorescence emission spectrum is centered on 440 nm. In addition to the photopic and scotopic systems, humans have other systems for detecting light that do not contribute to

1640-495: Is at about 590 nm. Mantis shrimp exhibit up to 14 opsins, enabling a visible range of less than 300 nm to above 700 nm. Some snakes can "see" radiant heat at wavelengths between 5 and 30  μm to a degree of accuracy such that a blind rattlesnake can target vulnerable body parts of the prey at which it strikes, and other snakes with the organ may detect warm bodies from a meter away. It may also be used in thermoregulation and predator detection. Spectroscopy

1722-412: Is composed of about 50% infrared light, 40% visible light, and 10% ultraviolet light, for a total intensity of about 1400 W/m 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

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1804-448: Is generally done in gasses (e.g. krypton, hydrogen which are two-photon resonant near 193 nm) or metal vapors (e.g. magnesium). By making one of the lasers tunable, the V‑UV can be tuned. If one of the lasers is resonant with a transition in the gas or vapor then the V‑UV production is intensified. However, resonances also generate wavelength dispersion, and thus the phase matching can limit

1886-497: 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. 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 radiation, in particular UVB radiation, has been shown to induce cell cycle arrest in keratinocytes ,

1968-490: Is mediated by rod cells . Each of these functions have different visible ranges. However, discussion on the visible range generally assumes photopic vision. The visible range of most animals evolved to match the optical window , which is the range of light that can pass through the atmosphere. The ozone layer absorbs almost all UV light (below 315 nm). However, this only affects cosmic light (e.g. sunlight ), not terrestrial light (e.g. Bioluminescence ). Before reaching

2050-419: Is no doubt that a little sunlight is good for you! But 5–15 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. Vitamin D can also be obtained from food and supplementation. Excess sun exposure produces harmful effects, however. Vitamin D promotes the creation of serotonin . The production of serotonin

2132-513: 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. Synchrotron light sources can also produce all wavelengths of UV, including those at the boundary of the UV and X‑ray spectra at 10 nm. The impact of ultraviolet radiation on human health has implications for

2214-498: Is planned to be used to calibrate the color cameras for the 2019 ESA Mars rover mission, since they will remain unfaded by the high level of UV present at the surface of Mars. Common soda–lime glass , such as window glass, is partially transparent to UVA, but is opaque to shorter wavelengths, passing about 90% of the light above 350 nm, but blocking over 90% of the light below 300 nm. A study found that car windows allow 3–4% of ambient UV to pass through, especially if

2296-716: Is sometimes reported to have a peak wavelength above 600 nm, but this is an effective peak wavelength that incorporates the filter of avian oil droplets . The peak wavelength of the LWS opsin alone is the better predictor of the long-wave limit. A possible benefit of avian UV vision involves sex-dependent markings on their plumage that are visible only in the ultraviolet range. Teleosts (bony fish) are generally tetrachromatic. The sensitivity of fish UVS opsins vary from 347-383 nm, and LWS opsins from 500-570 nm. However, some fish that use alternative chromophores can extend their LWS opsin sensitivity to 625 nm. The popular belief that

2378-419: Is the study of objects based on the spectrum of color they emit, absorb or reflect. Visible-light spectroscopy is an important tool in astronomy (as is spectroscopy at other wavelengths), where scientists use it to analyze the properties of distant objects. Chemical elements and small molecules can be detected in astronomical objects by observing emission lines and absorption lines . For example, helium

2460-446: Is visible to insects, some mammals, and some birds . Birds have a fourth color receptor for ultraviolet rays; this, coupled with eye structures that transmit more UV gives smaller birds "true" UV vision. "Ultraviolet" means "beyond violet" (from Latin ultra , "beyond"), violet being the color of the highest frequencies of visible light . Ultraviolet has a higher frequency (thus a shorter wavelength) than violet light. UV radiation

2542-540: The UV degradation (photo-oxidation) of a material. The absorbers can themselves degrade over time, so monitoring of absorber levels in weathered materials is necessary. In sunscreen , ingredients that absorb UVA/UVB rays, such as avobenzone , oxybenzone and octyl methoxycinnamate , are organic chemical absorbers or "blockers". They are contrasted with inorganic absorbers/"blockers" of UV radiation such as carbon black , titanium dioxide , and zinc oxide . For clothing,

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2624-399: 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, UV (specifically, UVB) is also responsible for the formation of vitamin D in most land vertebrates , including humans. The UV spectrum, thus, has effects both beneficial and detrimental to life. The lower wavelength limit of

2706-440: The lens . Insensitivity to IR light is limited by the spectral sensitivity functions of the visual opsins. The range is defined psychometrically by the luminous efficiency function , which accounts for all of these factors. In humans, there is a separate function for each of two visual systems, one for photopic vision , used in daylight, which is mediated by cone cells , and one for scotopic vision , used in dim light, which

2788-404: The retina , light must first transmit through the cornea and lens . UVB light (< 315 nm) is filtered mostly by the cornea, and UVA light (315–400 nm) is filtered mostly by the lens. The lens also yellows with age, attenuating transmission most strongly at the blue part of the spectrum. This can cause xanthopsia as well as a slight truncation of the short-wave (blue) limit of

2870-462: The ultraviolet protection factor (UPF) represents the ratio of sunburn -causing UV without and with the protection of the fabric, similar to sun protection factor (SPF) ratings for sunscreen . Standard summer fabrics have UPFs around 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

2952-419: The visible spectrum is conventionally taken as 400 nm, so ultraviolet rays are not visible to humans , although people can sometimes perceive light at shorter wavelengths than this. Insects, birds, and some mammals can see near-UV (NUV), i.e., slightly shorter wavelengths than what humans can see. Ultraviolet rays are usually invisible to most humans. The lens of the human eye blocks most radiation in

3034-427: The 17th century, Isaac Newton discovered that prisms could disassemble and reassemble white light, and described the phenomenon in his book Opticks . He was the first to use the word spectrum ( Latin for "appearance" or "apparition") in this sense in print in 1671 in describing his experiments in optics . Newton observed that, when a narrow beam of sunlight strikes the face of a glass prism at an angle, some

3116-646: The EUV spectrum is set by a prominent He spectral line at 30.4 nm. EUV is strongly absorbed by most known materials, but synthesizing multilayer optics that reflect up to about 50% of EUV radiation at normal incidence is possible. This technology was pioneered by the NIXT and MSSTA sounding rockets in the 1990s, and it has been used to make telescopes for solar imaging. See also the Extreme Ultraviolet Explorer satellite . Some sources use

3198-472: The L-opsin, there are also reports that pulsed NIR lasers can evoke green, which suggests two-photon absorption may be enabling extended NIR sensitivity. Similarly, young subjects may perceive ultraviolet wavelengths down to about 310–313 nm, but detection of light below 380 nm may be due to fluorescence of the ocular media, rather than direct absorption of UV light by the opsins. As UVA light

3280-431: The Sun, are absorbed by oxygen and generate the ozone in the ozone layer when single oxygen atoms produced by UV photolysis 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. Ultraviolet absorbers are molecules used in organic materials ( polymers , paints , etc.) to absorb UV radiation to reduce

3362-557: The UV spectrum. Sensitive UV photomultipliers are available. Spectrometers and radiometers are made for measurement of UV radiation. Silicon detectors are used across the spectrum. Vacuum UV, or VUV, wavelengths (shorter than 200 nm) are strongly absorbed by molecular oxygen in the air, though the longer wavelengths around 150–200 nm can propagate through nitrogen . Scientific instruments can, therefore, use this spectral range by operating in an oxygen-free atmosphere (pure nitrogen, or argon for shorter wavelengths), without

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3444-674: The UV was greater than 380 nm. Other types of car windows can reduce transmission of UV that is greater than 335 nm. Fused quartz , depending on quality, can be transparent even to vacuum UV wavelengths. Crystalline quartz and some crystals such as CaF 2 and MgF 2 transmit well down to 150 nm or 160 nm wavelengths. Wood's glass is a deep violet-blue barium-sodium silicate glass with about 9% nickel(II) oxide developed during World War I to block visible light for covert communications. It allows both infrared daylight and ultraviolet night-time communications by being transparent between 320 nm and 400 nm and also

3526-831: The UVA spectrum. The rated wavelength is the peak wavelength that the LEDs put out, but light at both higher and lower wavelengths are present. The cheaper and more common 395 nm UV LEDs are much closer to the visible spectrum, and give off a purple color. Other UV LEDs deeper into the spectrum do not emit as much visible light. LEDs are used for applications such as UV curing applications, charging glow-in-the-dark objects such as paintings or toys, and lights for detecting counterfeit money and bodily fluids. UV LEDs are also used in digital print applications and inert UV curing environments. Power densities approaching 3 W/cm (30 kW/m ) are now possible, and this, coupled with recent developments by photo-initiator and resin formulators, makes

3608-484: The UVC band at 253.7 nm and 185 nm due to the mercury 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

3690-489: The area around the Sun which appears white because the light is not scattered as much). The optical window is also referred to as the "visible window" because it overlaps the human visible response spectrum. The near infrared (NIR) window lies just out of the human vision, as well as the medium wavelength infrared (MWIR) window, and the long-wavelength or far-infrared (LWIR or FIR) window, although other animals may perceive them. Colors that can be produced by visible light of

3772-584: 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 ultraviolet index 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

3854-403: 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 tanning lamps and reptile-husbandry. Shortwave UV lamps are made using a fluorescent lamp tube with no phosphor coating, composed of fused quartz or vycor , since ordinary glass absorbs UVC. These lamps emit ultraviolet light with two peaks in

3936-614: The common goldfish is the only animal that can see both infrared and ultraviolet light is incorrect, because goldfish cannot see infrared light. The visual systems of invertebrates deviate greatly from vertebrates, so direct comparisons are difficult. However, UV sensitivity has been reported in most insect species. Bees and many other insects can detect ultraviolet light, which helps them find nectar in flowers. Plant species that depend on insect pollination may owe reproductive success to their appearance in ultraviolet light rather than how colorful they appear to humans. Bees' long-wave limit

4018-458: The days of the week. The human eye is relatively insensitive to indigo's frequencies, and some people who have otherwise-good vision cannot distinguish indigo from blue and violet. For this reason, some later commentators, including Isaac Asimov , have suggested that indigo should not be regarded as a color in its own right but merely as a shade of blue or violet. Evidence indicates that what Newton meant by "indigo" and "blue" does not correspond to

4100-460: The definition of the limits is not standard and will change depending on the industry. For example, some industries may be concerned with practical limits, so would conservatively report 420–680 nm, while others may be concerned with psychometrics and achieving the broadest spectrum would liberally report 380–750, or even 380–800 nm. The luminous efficiency function in the NIR does not have

4182-526: The development of solar-blind devices has been an important area of research. Wide-gap solid-state devices or vacuum devices with high-cutoff photocathodes can be attractive compared to silicon diodes. Extreme UV (EUV or sometimes XUV) is characterized by a transition in the physics of interaction with matter. Wavelengths longer than about 30 nm interact mainly with the outer valence electrons of atoms, while wavelengths shorter than that interact mainly with inner-shell electrons and nuclei. The long end of

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4264-581: The distinction of "hard UV" and "soft UV". For instance, in the case of astrophysics , the boundary may be at the Lyman limit (wavelength 91.2 nm, the energy needed to ionise a hydrogen atom from its ground state), with "hard UV" being more energetic; the same terms may also be used in other fields, such as cosmetology , optoelectronic , etc. The numerical values of the boundary between hard/soft, even within similar scientific fields, do not necessarily coincide; for example, one applied-physics publication used

4346-434: The early 19th century, the concept of the visible spectrum became more definite, as light outside the visible range was discovered and characterized by William Herschel ( infrared ) and Johann Wilhelm Ritter ( ultraviolet ), Thomas Young , Thomas Johann Seebeck , and others. Young was the first to measure the wavelengths of different colors of light, in 1802. The connection between the visible spectrum and color vision

4428-463: The emitting sources in UV spectroscopy equipment for chemical analysis. Other UV sources with more continuous emission spectra include xenon arc lamps (commonly used as sunlight simulators), deuterium arc lamps , mercury-xenon arc lamps , and metal-halide arc lamps . The excimer lamp , 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

4510-575: The entire UV range. The nitrogen gas laser 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 nm in wavelength. Another type of high-power gas lasers are excimer lasers . They are widely used lasers emitting in ultraviolet and vacuum ultraviolet wavelength ranges. Presently, UV argon-fluoride excimer lasers operating at 193 nm are routinely used in integrated circuit production by photolithography . The current wavelength limit of production of coherent UV

4592-482: The expansion of LED cured UV materials likely. UVC LEDs are developing rapidly, but may require testing to verify effective disinfection. Citations for large-area disinfection are for non-LED UV sources known as germicidal lamps . Also, they are used as line sources to replace deuterium lamps in liquid chromatography instruments. Gas lasers , laser diodes , and solid-state lasers can be manufactured to emit ultraviolet rays, and lasers are available that cover

4674-582: 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 small fraction of a percent of their power as UV. Mercury-vapor 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 fluorescence ,

4756-544: The ground right into early summer and sun positions even at zenith are low, are particularly at risk. Skin, the circadian system, and the immune system can also be affected. The 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 lighter skinned individuals being more sensitive) at wavelengths starting near

4838-408: 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 V‑UV wavelengths down to 75 nm was achieved using window-free configurations. Lasers have been used to indirectly generate non-coherent extreme UV (E‑UV) radiation at 13.5 nm for extreme ultraviolet lithography . The E‑UV

4920-475: The lens, mice have a UVS opsin that can detect down to 340 nm. While allowing UV light to reach the retina can lead to retinal damage, the short lifespan of mice compared with other mammals may minimize this disadvantage relative to the advantage of UV vision. Dogs have two cone opsins at 429 nm and 555 nm, so see almost the entire visible spectrum of humans, despite being dichromatic. Horses have two cone opsins at 428 nm and 539 nm, yielding

5002-406: The link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=VUV&oldid=1031664519 " Category : Disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages Vacuum UV Ultraviolet radiation , also known as simply UV ,

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5084-419: The longer infrared and just-barely-visible red wavelengths. Its maximum UV transmission is at 365 nm, one of the wavelengths of mercury lamps . A black light lamp emits long-wave UVA radiation and little visible light. Fluorescent black light lamps work similarly to other fluorescent lamps , but use a phosphor on the inner tube surface which emits UVA radiation instead of visible light. Some lamps use

5166-568: The minimum energy required to ionize atoms . Although long-wavelength ultraviolet is not considered an ionizing radiation because its photons lack sufficient energy, it can induce chemical reactions and cause many substances to glow or fluoresce . Many practical applications, including chemical and biological effects, are derived from the way that UV radiation can interact with organic molecules. These interactions can involve absorption or adjusting energy states in molecules, but do not necessarily involve heating. Short-wave ultraviolet light

5248-416: The modern meanings of those color words. Comparing Newton's observation of prismatic colors with a color image of the visible light spectrum shows that "indigo" corresponds to what is today called blue, whereas his "blue" corresponds to cyan . In the 18th century, Johann Wolfgang von Goethe wrote about optical spectra in his Theory of Colours . Goethe used the word spectrum ( Spektrum ) to designate

5330-473: The most common type of skin cell. As such, sunlight therapy can be a candidate for treatment of conditions such as psoriasis and exfoliative cheilitis , conditions in which skin cells divide more rapidly than usual or necessary. 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 areas where snow covers

5412-486: The need for costly vacuum chambers. Significant examples include 193-nm photolithography equipment (for semiconductor manufacturing ) and circular dichroism spectrometers. Technology for VUV instrumentation was largely driven by solar astronomy for many decades. While optics can be used to remove unwanted visible light that contaminates the VUV, in general, detectors can be limited by their response to non-VUV radiation, and

5494-458: The peak wavelengths of opsins with those of typical humans (S-opsin at 420 nm and L-opsin at 560 nm). Most mammals have retained only two opsin classes (LWS and VS), due likely to the nocturnal bottleneck . However, old world primates (including humans) have since evolved two versions in the LWS class to regain trichromacy. Unlike most mammals, rodents' UVS opsins have remained at shorter wavelengths. Along with their lack of UV filters in

5576-405: The position of the individual opsin spectral sensitivity functions therefore affects the luminous efficiency function and the visible range. For example, the long-wave (red) limit changes proportionally to the position of the L-opsin. The positions are defined by the peak wavelength (wavelength of highest sensitivity), so as the L-opsin peak wavelength blue shifts by 10 nm, the long-wave limit of

5658-454: The previous year 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 John William Draper , who named them "tithonic rays" ). The terms "chemical rays" and "heat rays" were eventually dropped in favor of ultraviolet and infrared radiation , respectively. In 1878,

5740-459: The primary visual system . For example, melanopsin has an absorption range of 420–540 nm and regulates circadian rhythm and other reflexive processes. Since the melanopsin system does not form images, it is not strictly considered vision and does not contribute to the visible range. The visible spectrum is defined as that visible to humans, but the variance between species is large. Not only can cone opsins be spectrally shifted to alter

5822-479: The prism, creating a spectrum of colors. Newton originally divided the spectrum into six named colors: red , orange , yellow , green , blue , and violet . He later added indigo as the seventh color since he believed that seven was a perfect number as derived from the ancient Greek sophists , of there being a connection between the colors, the musical notes, the known objects in the Solar System , and

5904-515: The risks and benefits of sun exposure and is also implicated in issues such as fluorescent lamps and health . Getting too much sun exposure can be harmful, but in moderation, sun exposure is beneficial. UV (specifically, UVB) causes the body to produce vitamin D , which is essential for life. Humans need some UV radiation to maintain adequate vitamin D levels. According to the World Health Organization: There

5986-462: The same way as the visible blue light from those parts of the sky. UVB also plays a major role in plant development, as it affects most of the plant hormones. During total overcast, the amount of absorption due to clouds is heavily dependent on the thickness of the clouds and latitude, with no clear measurements correlating specific thickness and absorption of UVA and UVB. The shorter bands of UVC, as well as even more-energetic UV radiation produced by

6068-586: The sterilizing effect of short-wavelength light by killing bacteria was discovered. By 1903, the most effective wavelengths were known to be 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 German physicist Victor Schumann . The electromagnetic spectrum of ultraviolet radiation (UVR), defined most broadly as 10–400 nanometers, can be subdivided into

6150-478: The tunable range of the 4 wave mixing. Difference frequency mixing (i.e., f 1 + f 2 − f 3 ) has an advantage over sum frequency mixing because the phase matching can provide greater tuning. In particular, difference frequency mixing two photons of an Ar F (193 nm) excimer laser with a tunable visible or near IR laser in hydrogen or krypton provides resonantly enhanced tunable V‑UV covering from 100 nm to 200 nm. Practically,

6232-500: The ultraviolet radiation that reaches the Earth's surface, more than 95% is the longer wavelengths of UVA, with the small remainder UVB. Almost no UVC reaches the Earth's surface. The fraction of UVA and UVB which remains in UV radiation after passing through the atmosphere is heavily dependent on cloud cover and atmospheric conditions. On "partly cloudy" days, patches of blue sky showing between clouds are also sources of (scattered) UVA and UVB, which are produced by Rayleigh scattering in

6314-405: The visible range, but vertebrates with 4 cones (tetrachromatic) or 2 cones (dichromatic) relative to humans' 3 (trichromatic) will also tend to have a wider or narrower visible spectrum than humans, respectively. Vertebrates tend to have 1-4 different opsin classes: Testing the visual systems of animals behaviorally is difficult, so the visible range of animals is usually estimated by comparing

6396-532: The visible spectrum also shifts 10 nm. Large deviations of the L-opsin peak wavelength lead to a form of color blindness called protanomaly and a missing L-opsin ( protanopia ) shortens the visible spectrum by about 30 nm at the long-wave limit. Forms of color blindness affecting the M-opsin and S-opsin do not significantly affect the luminous efficiency function nor the limits of the visible spectrum. Regardless of actual physical and biological variance,

6478-433: The visible spectrum. Subjects with aphakia are missing a lens, so UVA light can reach the retina and excite the visual opsins; this expands the visible range and may also lead to cyanopsia . Each opsin has a spectral sensitivity function, which defines how likely it is to absorb a photon of each wavelength. The luminous efficiency function is approximately the superposition of the contributing visual opsins . Variance in

6560-476: The wavelength range of 300–400 nm; shorter wavelengths are blocked by the cornea . Humans also lack color receptor adaptations for ultraviolet rays. Nevertheless, the photoreceptors of the retina are sensitive to near-UV, and people lacking a lens (a condition known as aphakia ) perceive near-UV as whitish-blue or whitish-violet. Under some conditions, children and young adults can see ultraviolet down to wavelengths around 310 nm. Near-UV radiation

6642-657: Was discovered in February 1801 when the German physicist Johann Wilhelm Ritter observed that invisible rays just beyond the violet end of the visible spectrum darkened silver chloride -soaked paper more quickly than violet light itself. He announced the discovery in a very brief letter to the Annalen der Physik and later called them "(de-)oxidizing rays" ( German : de-oxidierende Strahlen ) to emphasize chemical reactivity and to distinguish them from " heat rays ", discovered

6724-414: Was explored by Thomas Young and Hermann von Helmholtz in the early 19th century. Their theory of color vision correctly proposed that the eye uses three distinct receptors to perceive color. The visible spectrum is limited to wavelengths that can both reach the retina and trigger visual phototransduction (excite a visual opsin ). Insensitivity to UV light is generally limited by transmission through

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