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93-408: When observed in the ultraviolet and mid- infrared , the central region and bar of NGC 6872 show old stars and low rates of star formation , with rates increasing along the spiral arms as distance from the core increases. The most active region of star formation, located in the northeast arm, shows a stellar flux around 1,000 times higher than in the central region, though this may be affected by

186-427: A UV-A light , Wood's lamp , or ultraviolet light , is a lamp that emits long-wave ( UV-A ) ultraviolet light and very little visible light . One type of lamp has a violet filter material, either on the bulb or in a separate glass filter in the lamp housing, which blocks most visible light and allows through UV, so the lamp has a dim violet glow when operating. Blacklight lamps which have this filter have

279-482: A phosphor that emits UVA light instead of visible white light is used on the inside of the tube. The type most commonly used for blacklights, designated blacklight blue or "BLB" by the industry, has a dark blue filter coating on the tube, which filters out most visible light, so that fluorescence effects can be observed. These tubes have a dim violet glow when operating. They should not be confused with "blacklight" or "BL" tubes, which have no filter coating, and have

372-468: A 290–330-thousand-light-year (90–100 kpc) X-ray trail that exists between NGC 6872 and the nearby elliptical galaxy NGC 6876 . NGC 6872 is moving away from NGC 6876 at 849 ± 28 km/s (528 ± 17 mi/s) in approximately the same trajectory as the X-ray trail, suggesting a link between the two galaxies. Four possibilities for the trail's existence were given: gas stripped from

465-436: A Kill . Blacklight puppetry is performed in a blacklight theater. Blacklights are a common tool for rock-hunting and identification of minerals by their fluorescence. The most common minerals and rocks that glow under UV light are fluorite, calcite, aragonite, opal, apatite, chalcedony, corundum (ruby and sapphire), scheelite, selenite, smithsonite, sphalerite, sodalite. The first person to observe fluorescence in minerals

558-483: 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 )

651-433: A brighter blue color. These are made for use in " bug zapper " insect traps where the emission of visible light does not interfere with the performance of the product. The phosphor typically used for a near 368 to 371 nanometer emission peak is either europium -doped strontium fluoroborate ( SrB 2 F 8 : Eu ) or europium-doped strontium borate ( Sr 3 B 2 O 6 : Eu ) while

744-433: 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

837-529: A few arcseconds away, and is known to be interacting with NGC 6872. Horrelou and Koribalski (2007), using a computer simulation to determine how the two galaxies were interacting, reported that IC 4970 approached NGC 6872 nearly along the plane of its spiral disk, making its closest approach approximately 130 million years ago and resulting in the latter's current highly elongated shape. An ultraviolet-to-infrared study by Eufrasio, et al. (2013), using data from GALEX , Spitzer , and other resources found that

930-671: 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

1023-536: 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. Black light A blacklight , also called

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1116-506: A light source is referred to as a Wood's lamp, named after Robert Williams Wood , who invented the original Wood's glass UV filters. Although many other types of lamp emit ultraviolet light with visible light, blacklights are essential when UV-A light without visible light is needed, particularly in observing fluorescence , the colored glow that many substances emit when exposed to UV. They are employed for decorative and artistic lighting effects, diagnostic and therapeutic uses in medicine,

1209-633: A lighting industry designation that includes the letters "BLB". This stands for "blacklight blue". A second type of lamp produces ultraviolet but does not have the filter material, so it produces more visible light and has a blue color when operating. These tubes are made for use in " bug zapper " insect traps, and are identified by the industry designation "BL". This stands for "blacklight". Blacklight sources may be specially designed fluorescent lamps , mercury-vapor lamps , light-emitting diodes (LEDs), lasers , or incandescent lamps . In medicine , forensics , and some other scientific fields, such

1302-545: 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

1395-481: A photochemical reaction inside those substances. This process of hardening is called ‘curing’. UV curing is adaptable to printing, coating, decorating, stereolithography, and in the assembly of a variety of products and materials. In comparison to other technologies, curing with UV energy may be considered a low-temperature process, a high-speed process, and is a solventless process, as cure occurs via direct polymerization rather than by evaporation. Originally introduced in

1488-581: A soft tip, that can be used to "invisibly" mark items. If the objects that are so marked are subsequently stolen, a blacklight can be used to search for these security markings. At some amusement parks , nightclubs and at other, day-long (or night-long) events, a fluorescent mark is rubber stamped onto the wrist of a guest who can then exercise the option of leaving and being able to return again without paying another admission fee. Fluorescent materials are also very widely used in numerous applications in molecular biology, often as "tags" which bind themselves to

1581-414: A substance of interest (for example, DNA), so allowing their visualization. Thousands of moth and insect collectors all over the world use various types of blacklights to attract moth and insect specimens for photography and collecting. It is one of the preferred light sources for attracting insects and moths at night. They can illuminate animal excreta, such as urine and vomit, that is not always visible to

1674-520: 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

1767-449: 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

1860-469: 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

1953-1048: 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

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2046-517: Is absorbed less and reaches deeper into skin layers , where it produces reactive chemical intermediates such as hydroxyl and oxygen radicals , which in turn can damage DNA and result in a risk of melanoma . The weak output of blacklights is not sufficient to cause DNA damage or cellular mutations in the way that direct summer sunlight can, although there are reports that overexposure to the type of UV radiation used for creating artificial suntans on sunbeds can cause DNA damage, photo-aging (damage to

2139-804: Is also helpful in diagnosing: A Wood's lamp may be used to rapidly assess whether an individual is suffering from ethylene glycol poisoning as a consequence of antifreeze ingestion. Manufacturers of ethylene glycol-containing antifreezes commonly add fluorescein , which causes the patient's urine to fluoresce under Wood's lamp. Wood's lamp is useful in diagnosing conditions such as tuberous sclerosis and erythrasma (caused by Corynebacterium minutissimum , see above). Additionally, detection of porphyria cutanea tarda can sometimes be made when urine turns pink upon illumination with Wood's lamp. Wood's lamps have also been used to differentiate hypopigmentation from depigmentation such as with vitiligo . A vitiligo patient's skin will appear yellow-green or blue under

2232-533: Is called fluorescence , and has many practical uses. Blacklights are required to observe fluorescence, since other types of ultraviolet lamps emit visible light which drowns out the dim fluorescent glow. A Wood's lamp is a diagnostic tool used in dermatology by which ultraviolet light is shone (at a wavelength of approximately 365 nanometers) onto the skin of the patient; a technician then observes any subsequent fluorescence . For example, porphyrins —associated with some skin diseases—will fluoresce pink. Though

2325-412: 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

2418-454: Is designed for use in bug zappers . Insects are attracted to the UV light, which they are able to see, and are then electrocuted by the device. These bulbs use the same UV-A emitting phosphor blend as the filtered blacklight, but since they do not need to suppress visible light output, they do not use a purple filter material in the bulb. Plain glass blocks out less of the visible mercury emission spectrum, making them appear light blue-violet to

2511-448: 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

2604-497: 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 ,

2697-419: 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

2790-513: 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

2883-498: 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

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2976-409: 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

3069-498: Is that less space needs to be devoted to storing items which can not be used until the drying step is finished. Because UV energy has unique interactions with many different materials, UV curing allows for the creation of products with characteristics not achievable via other means. This has led to UV curing becoming fundamental in many fields of manufacturing and technology, where changes in strength, hardness, durability, chemical resistance, and many other properties are required. One of

3162-417: Is then run in order to circulate the dye across the piping and components and then the system is examined with a blacklight lamp. Any evidence of fluorescent dye then pinpoints the leaking part which needs replacement. Blacklight is used to illuminate pictures painted with fluorescent colors, particularly on black velvet , which intensifies the illusion of self-illumination. The use of such materials, often in

3255-446: 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

3348-537: 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,

3441-466: The World Health Organization , UV-A is responsible for the initial tanning of skin and it contributes to skin ageing and wrinkling. UV-A may also contribute to the progression of skin cancers. Additionally, UV-A can have negative effects on eyes in both the short-term and long-term. Fluorescent blacklight tubes are typically made in the same fashion as normal fluorescent tubes except that

3534-399: 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

3627-462: 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

3720-419: 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

3813-498: The 1960s, this technology has streamlined and increased automation in many industries in the manufacturing sector. A primary advantage of curing with ultraviolet light is the speed at which a material can be processed. Speeding up the curing or drying step in a process can reduce flaws and errors by decreasing time that an ink or coating spends wet. This can increase the quality of a finished item, and potentially allow for greater consistency. Another benefit to decreasing manufacturing time

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3906-627: 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

3999-431: 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

4092-557: 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

4185-674: 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

4278-827: 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

4371-526: The UVB range. UVA is the safest of the three spectra of UV light , although high exposure to UVA has been linked to the development of skin cancer in humans. The relatively low energy of UVA light does not cause sunburn . It can damage collagen fibers, so may accelerate skin aging and cause wrinkles . It can also degrade vitamin A in the skin. UVA light has been shown to cause DNA damage , but not directly, like UVB and UVC. Due to its longer wavelength , it

4464-481: 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

4557-455: The Wood's lamp. Its use in detecting melanoma has been reported. Blacklight is commonly used to authenticate oil paintings , antiques and banknotes . It can also differentiate real currency from counterfeit notes because, in many countries, legal banknotes have fluorescent symbols on them that only show under a blacklight. In addition, the paper used for printing money does not contain any of

4650-535: 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

4743-432: The best sources of fluorite in mines or potential new mines. Some transparent selenite crystals exhibit an “hourglass” pattern under UV light that is not visible in natural light. These crystals are also phosphorescent. Limestone, marble, and travertine can glow because of calcite presence. Granite, syenite, and granitic pegmatite rocks can also glow. UV light can be used to harden particular glues, resins and inks by causing

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4836-411: The brightening agents which cause commercially available papers to fluoresce under blacklight. Both of these features make illegal notes easier to detect and more difficult to successfully counterfeit. The same security features can be applied to identification cards such as passports or driver's licenses . Other security applications include the use of pens containing a fluorescent ink, generally with

4929-403: 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

5022-419: The density of stellar dust in the core. The extended portions of both arms exhibit young star cluster formations with ages ranging from one to one hundred million years. Star formation rates in the northeast extended arm are twice that of the southwest extended arm, and five times the formation rate in the sections of the arms closer to the central region. IC 4970 is a nearby lenticular galaxy , located only

5115-470: The detection of substances tagged with fluorescent dyes , rock-hunting , scorpion-hunting, the detection of counterfeit money , the curing of plastic resins, attracting insects and the detection of refrigerant leaks affecting refrigerators and air conditioning systems. Strong sources of long-wave ultraviolet light are used in tanning beds . UV-A presents a potential hazard when eyes and skin are exposed, especially to high power sources. According to

5208-526: 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

5301-577: 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

5394-427: The emission peaks are broad, so only the very lowest energy UV photons are emitted, within predominant not visible light. Although blacklights produce light in the UV range, their spectrum is mostly confined to the longwave UVA region, that is, UV radiation nearest in wavelength to visible light, with low frequency and therefore relatively low energy. While low, there is still some power of a conventional blacklight in

5487-463: 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

5580-575: 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

5673-482: 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

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5766-582: 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 ,

5859-445: The eyes and skin. A few other spectral lines, falling within the pass band of the Wood's glass between 300 and 400 nm, contribute to the output. These lamps are used mainly for theatrical purposes and concert displays. They are more efficient UVA producers per unit of power consumption than fluorescent tubes. Ultraviolet light can be generated by some light-emitting diodes , but wavelengths shorter than 380 nm are uncommon, and

5952-509: The form of tiles viewed in a sensory room under UV light, is common in the United Kingdom for the education of students with profound and multiple learning difficulties. Such fluorescence from certain textile fibers, especially those bearing optical brightener residues, can also be used for recreational effect, as seen, for example, in the opening credits of the James Bond film A View to

6045-544: 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

6138-463: The innovations for night and all-weather flying used by the US, UK, Japan and Germany during World War II was the use of UV interior lighting to illuminate the instrument panel, giving a safer alternative to the radium -painted instrument faces and pointers, and an intensity that could be varied easily and without visible illumination that would give away an aircraft's position. This went so far as to include

6231-429: The intensified and slightly broadened 350–375 nm spectral line of mercury from high pressure discharge at between 5 and 10 standard atmospheres (500 and 1,000 kPa), depending upon the specific type. These lamps use envelopes of Wood's glass or similar optical filter coatings to block out all the visible light and also the short wavelength (UVC) lines of mercury at 184.4 and 253.7 nm, which are harmful to

6324-408: The interaction between the two galaxies appears to have triggered significant star formation in the northeastern arm of NGC 6872 beginning about 130 thousand light-years (40 kpc) from its nucleus. The same appears to have also occurred in the southwestern arm. A bright ultraviolet source was discovered at the end of the northeastern arm, around 290 thousand light-years (90 kpc) from

6417-408: 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

6510-419: 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

6603-568: 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

6696-473: 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

6789-403: The naked eye. Blacklight is used extensively in non-destructive testing. Fluorescing fluids are applied to metal structures and illuminated, allowing easy detection of cracks and other weaknesses. If a leak is suspected in a refrigerator or an air conditioning system, a UV tracer dye can be injected into the system along with the compressor lubricant oil and refrigerant mixture. The system

6882-403: The naked eye. These lamps are referred to by the designation "blacklight" or "BL" in some North American lighting catalogs. These types are not suitable for applications which require the low visible light output of "BLB" tubes lamps. A blacklight may also be formed by simply using a UV filter coating such as Wood's glass on the envelope of a common incandescent bulb . This was the method that

6975-458: The necessary absorption of the visible light, become very hot during use. This heat is, in fact, encouraged in such bulbs, since a hotter filament increases the proportion of UVA in the black-body radiation emitted. This high running-temperature reduces the life of the lamp from a typical 1,000 hours to around 100 hours. High-power mercury vapor blacklight lamps are made in power ratings of 100 to 1,000 watts. These do not use phosphors, but rely on

7068-483: 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

7161-515: The nucleus, which may be a tidal dwarf galaxy formed out of the interaction between IC 4970 and NGC 6872 . The bright ultraviolet nature of this cluster indicates that it contains stars less than 200 million years old, which roughly coincides with the timeframe of the collision. Mihos, et al. (1993), and Eufrasio, et al. (2014), suggest that prior to its interaction with IC 4970 , the galaxy's disk may have been non-uniform with an extended mass distribution. Machacek, et al. (2005), reported on

7254-407: The phosphor used to produce a peak around 350 to 353 nanometres is lead-doped barium silicate ( BaSi 2 O 5 : Pb ). "Blacklight blue" lamps peak at 365 nm. Manufacturers use different numbering systems for blacklight tubes. Philips' is becoming outdated (as of 2010), while the (German) Osram system is becoming dominant outside North America. The following table lists

7347-454: 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,

7440-502: 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

7533-462: 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

7626-428: The skin from prolonged exposure to sunlight), toughening of the skin, suppression of the immune system, cataract formation and skin cancer. UV-A can have negative effects on eyes in both the short-term and long-term. Ultraviolet radiation is invisible to the human eye, but illuminating certain materials with UV radiation causes the emission of visible light, causing these substances to glow with various colors. This

7719-586: 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

7812-405: The technique for producing a source of ultraviolet light was devised by Robert Williams Wood in 1903 using " Wood's glass ", it was in 1925 that the technique was used in dermatology by Margarot and Deveze for the detection of fungal infection of hair. It has many uses, both in distinguishing fluorescent conditions from other conditions and in locating the precise boundaries of the condition. It

7905-412: The trail. If NGC 6872 and NGC 6876 did interact in the past, the latter may have affected NGC 6872's spiral arms and gas distribution as much as its interaction with IC 4970 . Ultraviolet Ultraviolet radiation , also known as simply UV , is electromagnetic radiation of wavelengths of 10–400 nanometers , shorter than that of visible light , but longer than X-rays . UV radiation

7998-427: The tubes generating blue, UVA and UVB, in order of decreasing wavelength of the most intense peak. Approximate phosphor compositions, major manufacturer's type numbers and some uses are given as an overview of the types available. "Peak" position is approximated to the nearest 10 nm. "Width" is the measure between points on the shoulders of the peak that represent 50% intensity. Another class of UV fluorescent bulb

8091-478: 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,

8184-463: The two galaxies during a close fly-by, intergalactic medium that has been gravitationally focused behind NGC 6872 as it moves, interstellar medium that was stripped from NGC 6872 by ram pressure as it passed through the densest part of the Pavo group, and interstellar medium stripped from NGC 6872 by turbulent viscosity as it passes through Pavo. Any or all of these processes may be responsible for

8277-500: 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

8370-476: 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

8463-527: Was George Stokes in 1852. He noted the ability of fluorite to produce a blue glow when illuminated with ultraviolet light and called this phenomenon “fluorescence” after the mineral fluorite. Lamps used to visualise seams of fluorite and other fluorescent minerals are commonly used in mines but they tend to be on an industrial scale. The lamps need to be short wavelength to be useful for this purpose and of scientific grade. UVP range of hand held UV lamps are ideal for this purpose and are used by Geologists to identify

8556-643: 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

8649-411: Was used to create the very first blacklight sources. Although incandescent bulbs are a cheaper alternative to fluorescent tubes, they are exceptionally inefficient at producing UV light since most of the light emitted by the filament is visible light which must be blocked. Due to its black body spectrum, an incandescent light radiates less than 0.1% of its energy as UV light. Incandescent UV bulbs, due to

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