Ultraviolet ( UV ) is electromagnetic radiation with wavelengths from 10 nm to 400 nm, shorter than visible light but longer than X-rays. UV radiation is present in the sun which is about 10% of the total solar light output. It is also produced by electric arcs and special lights, such as mercury vapor lamps, tanning lamps, and black lights. Although long ultraviolet waves are not considered as ionizing radiation because their photons lack energy to ionize atoms, they can cause chemical reactions and cause many substances to sparkle or fluoresce. As a result, the chemical and biological effects of UV are greater than simple warming effects, and many practical applications of UV radiation come from their interactions with organic molecules.
Acne and sunburn are the familiar effects of excessive skin exposure to UV, along with a higher risk of skin cancer. Living things on dry land will be severely damaged by ultraviolet radiation from the Sun if largely unfiltered by Earth's atmosphere. The more-energetic, shorter-wavelength "extreme" UV below 121 nm ionizes the air so strong that it is absorbed before it reaches the ground. Ultraviolet is also responsible for the formation of vitamin D bone booster in most land vertebrates, including humans. The UV spectrum has beneficial effects and is harmful to human health.
Ultraviolet light is not visible to all humans, although insects, birds, and some mammals can see near-UV.
Video Ultraviolet
Visibility
Ultraviolet light is not seen by most humans. The human eye lens blocks most of the radiation in the wavelength range 300-400 Â ° nm; Shorter wavelengths are blocked by the cornea. Humans lack the adaptation of color receptors for ultraviolet light. Nevertheless, the retinal photoreceptors are sensitive to near-UV, and those with less lenses (a condition known as aphakia) see near-UV as a whitish blue or purple-violet. In some conditions, children and young adults may see ultraviolet to wavelengths of about 310Ã, nm. UV radiation is almost visible to insects, some mammals, and birds. Small birds have a fourth color receptor for ultraviolet light; this gives the bird a "true" UV vision.
Maps Ultraviolet
Discovery
"Ultraviolet" means "outside purple" (from Latin ultra , "outside"), purple is the color of the highest frequency of visible light. Ultraviolet has a higher frequency than purple light.
UV radiation was discovered in 1801 when German physicist Johann Wilhelm Ritter observed that invisible rays just beyond the purple end of the visible spectrum, silver chloride-colored paper soaked faster than the purple light itself. He called them "oxidizing rays" to emphasize chemical reactivity and distinguish it from "heat rays", finding the previous year at the other end of the visible spectrum. The simpler term "chemical beam" was adopted shortly thereafter, and remained popular throughout the nineteenth century, although there are those who argue that this is a completely different kind of radiation from light (especially John William Draper, who named them "rays tithonic "). The terms chemical rays and ultimately heat rays come down supporting ultraviolet and infrared radiation, respectively. In 1878 the effect of short wavelength sterilization of light by killing the bacteria was found. In 1903 it was known that the most effective wavelength was about 250 nm. In 1960, the effects of ultraviolet radiation on DNA were established.
The discovery of ultraviolet radiation with wavelengths below 200nm, named "ultraviolet vacuum" because it is so absorbed by air, was made in 1893 by German physicist Victor Schumann.
Subtype
The electromagnetic spectrum of ultraviolet radiation (UVR), which is defined broadest as 10-400 nanometers, can be divided into several ranges recommended by the ISO-21348 ISO standard:
Various solid-state and vacuum devices have been explored for use in different parts of the UV spectrum. Many approaches attempt to adjust visible light sensing devices, but these can suffer from unwanted responses to visible light and various instabilities. Ultraviolet can be detected by suitable photodiode and photocathode, which can be adjusted to be sensitive to different parts of the UV spectrum. Sensitive ultraviolet phototomultipliers are available. Spectrometers and radiometers are made for UV radiation measurements. Silicon detectors are used throughout the spectrum.
UV vacuum, or VUV, wavelength (shorter than 200 m) is strongly absorbed by oxygen molecules in the air, although longer wavelengths of about 150-200 nm can propagate through nitrogen. Therefore, scientific instruments can use this spectral range by operating in an oxygen-free atmosphere (usually pure nitrogen), without the need for expensive vacuum chambers. Significant examples include photonography equipment 193Ã, nm (for semiconductor manufacturing) and circular dichroism spectrometers.
The technology for VUV instrumentation is largely driven by solar astronomy for decades. While optics can be used to remove unwanted visible light that pollutes the VUV, in general, detectors can be limited by their response to non-VUV radiation, and the development of solar-blind devices has become an important field of research. Wide gap solid-state devices or vacuum devices with high cut-off photocathode 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 primarily with the outer valence electrons of atoms, while wavelengths are shorter than those that interact primarily with electrons and inner cell nuclei. The long end of the EUV spectrum is determined by the prominent He spectral lines at 30.4 nm. EUV is highly absorbed by the most recognizable material, but it is possible to synthesize multilayer optics that reflect up to about 50 percent of EUV radiation in normal events. This technology was spearheaded by NIXT and MSSTA sounding rockets in the 1990s, and has been used to make telescopes for solar imaging. See also Extreme Ultraviolet Explorer (EUVE) satellite.
Solar ultraviolet
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. A very hot star emits UV radiation proportionately from the Sun. Sunlight in the sky above the Earth's atmosphere (see the solar constant) consists of about 50% of infrared light, 40% visible light, and 10% of ultraviolet light, with a total intensity of about 1400 W/m 2 in vacuum.
However, in the sunlight at the soil surface is 44% visible light, 3% ultraviolet (with the Sun at its peak), and the rest is infrared. Thus, the atmosphere blocks about 77% of the UV of the Sun, almost entirely in shorter UV wavelengths, when the Sun is at its highest in the sky (zenith). Of the ultraviolet radiation reaching the Earth's surface, more than 95% is longer UVA wavelength, with small residual UVB. Basically no UVC. UVB fractions that remain in UV radiation after passing through the atmosphere are heavily dependent on cloud cover and atmospheric conditions. Thick clouds block UVB effectively, but in "partially cloudy", blue sky spots that show between clouds are also a source (spread) of UVA and UVB, which are generated by Rayleigh scattering in the same way as the visible blue light of the parts the. from the sky. UV-B also plays a major role in plant development because it affects most of the plant hormones.
The shorter UVC bands, as well as the more energetic UV radiation produced by the Sun, are absorbed by oxygen and produce ozone in the ozone layer when single oxygen atoms generated by UV dioxygenic photolysis react with more oxygen. The ozone layer is essential in blocking most UVB and residual parts of UVC that have not been blocked by ordinary oxygen in the air.
Inhibitors and silencers
Ultraviolet absorbers are molecules used in organic materials (polymers, paints, etc.) to absorb UV radiation to reduce UV (photo-oxidation) degradation of a material. The absorber itself can be degraded over time, so monitoring absorber levels in weather materials is required.
In sunscreen, materials that absorb UVA/UVB rays, such as avobenzone, oxybenzone, and octyl methoxycinnamate, are organic chemical absorbs or "blockers". They contrast with inorganic dampers/"blockers" of UV radiation such as carbon black, titanium dioxide and zinc oxide.
For clothing, the Ultraviolet Protection Factor (UPF) represents the ratio of UV to sunlight without and with fabric protection, similar to the Sun Protection Factor (SPF) rating for sunscreen. Standard summer fabrics have an UPF of about 6, which means that about 20% of the UV will pass through.
Nanoparticles suspended in stained glass prevent UV rays causing chemical reactions that change the color of the image. A set of stained glass reference chips is planned to be used to calibrate color cameras for the ESA Mars 2019 rover mission, as they will remain unaffected by the high levels of UV present on the surface of Mars.
Common soda-lime glass is partially transparent to UVA but is opaque with shorter wavelengths, whereas fused quartz glass, depending on quality, can be transparent even for UV wavelength vacuum. Ordinary window glass passes about 90% of light above 350 nm, but blocks more than 90% of light below 300 m.
Glass wood is a form of nickel glass with a purplish blue color that blocks the most visible light and passes through the ultraviolet.
Artificial source
"Black light"
The black lights light emits long wave UVA radiation and little visible light. Black fluorescent lights work in conjunction with other fluorescent lamps, but use phosphors on the surface of the inner tubes that emit UVA radiation, not visible light. Some lights use a blue-purple glassy optical glass filter that blocks most visible light with a wavelength of over 400 nanometers. Others use ordinary glass instead of more expensive Wood glass, making it look light blue to the eye while operating. Black lights can also be formed, very inefficiently, by using Wood's glass coating in envelopes for incandescent lamps. Although cheaper than a fluorescent UV lamp, only 0.1% of the input power is emitted as UV radiation can be used. The black glow of mercury-steam is ranked up to 1 kW with UV emitting phosphors and a Wood glass envelope used for theater and concert performances. Black lights are used in applications where visible foreign light should be minimized; especially to observe fluorescence, colored light that emits many substances when exposed to UV light. UVA/UVB emitting lamps are also sold for other special purposes, such as tanning lamps and reptiles.
Short-wave ultraviolet light
Short-wave UV lamps are made using a light bulb without a phosphor coating consisting of fused quartz, since ordinary glass absorbs UVC. These lights emit ultraviolet light with two peaks in the UVC band at 253.7 nm and 185 nm because of mercury in the lamp, as well as some visible light. From 85% to 90% of the UV produced by these lamps is 253,7Ã,nm, whereas only 5-10% at 185Ã, nm. The fused quartz glass tube passes through 253 nm radiation but blocks the wavelength of 185 nm. Such a tube has two or three times the strength of UVC from a regular fluorescent lamp tube. This low-pressure lamp has a typical efficiency of about 30-40%, which means that for every 100 watts of electricity consumed by the lamp, they will produce about 30-40 watts of total UV output. These "germicide" lamps are widely used for surface disinfection in laboratories and food processing industries, and for disinfection of water supplies.
The incandescent lamp has been used as an ultraviolet source with a filter layer on the bulb that absorbs most of the visible light. Halogen lamps with fused quartz envelopes are used as cheap UV light sources in the near UV range, from 400 to 300 nm, in some scientific instruments. Due to the black-body spectrum, the filament bulb is a very inefficient ultraviolet source, emitting only a fraction of the energy percent as UV.
Gas release lamp
Special UV gas discharge lamps containing different gases produce UV radiation on certain spectral lines for scientific purposes. Argon and deuterium arc lamps are often used as stable sources, either without windows or with windows like magnesium fluoride. It is often a source of transmitters in UV spectroscopy equipment for chemical analysis.
Other UV sources with continuous emission spectrum include xenon arc lamps (commonly used as solar simulators), deuterium arc lamps, mercury-xenon arc lamps, and metal halide bow lights.
The excimer lamps, the UV sources developed in the last two decades, are increasingly being used in the scientific field. It has the advantage of high intensity, high efficiency, and operation on various wavelength bands into ultraviolet vacuum.
Ultraviolet LED
Light emitting diodes (LEDs) can be produced to emit radiation in the ultraviolet range. The LED efficiency at 365Ã, nm is about 5-8%, while the efficiency at 395 n is closer to 20%, and the power output at longer UV wavelengths is also better. Such LED arrays are being used for UV hardening applications, and have been successful in digital printing applications and UV inert curing environments. Power densities close to 3Ã, W/cm 2 ) are now possible, and this, coupled with the latest developments by photoinitiator and resin formulator, made the expansion of UV-LED Material cured as possible.
UVC LEDs are being used in disinfection and as a line source for replacing deuterium lamps in liquid chromatography instruments.
Ultraviolet laser
Laser gases, diode lasers and solid-state lasers can be produced to emit ultraviolet light, and lasers are available that cover the entire UV range. The nitrogen gas laser uses an electronic excitation of nitrogen molecules to emit most UV rays. The strongest ultraviolet line is at 337.1 nm and 357,6,6 nm, wavelength. Another type of laser high-power laser is an excimer laser. They are widely used laser emitting in ultraviolet and ultraviolet wavelength range. Currently, an argon-fluoride (ARF) excimer laser operating at 193 nm is routinely used in the production of integrated circuits with photolithography. The current wavelength limit of UV coherent production is about 126 nm, excimer laser characteristic Ar 2 *.
Direct UV-emitting laser diodes are available at 375 nm. UV laser diodes have been shown using Ce: LiSAF crystals (cerium-doped lithium strontium aluminum fluoride), a process developed in the 1990s at the Lawrence Livermore National Laboratory. The wavelength is shorter than the commercially produced 325 m in the diode-pump solid-state laser. Ultraviolet lasers can also be made by applying frequency conversion to low frequency lasers.
Ultraviolet lasers have applications in the industry (laser engraving), medicine (dermatology, and keratectomy), chemical (MALDI), free air safe communications, computing (optical storage) and integrated circuit manufacturing.
Ultraviolet vacuum shimmer (VUV) through mixed number and frequency difference
The ultraviolet vacuum band (VUV) (100-200m) can be produced by mixing 4 non-linear waves in the gas by the summing or mixing frequency difference of 2 or more wavelength laser lengths. Generation is generally carried out in gases (eg krypton, hydrogen which is a two-photon resonon near 193Ã, nm) or metal vapor (eg magnesium). By making one of the tunable lasers, VUV can be set. If one of the lasers resonates with a transition in gas or steam then the VUV production is intensified. However, resonance also generates wavelength dispersion, and thus phase matching can limit the melodious range of 4 wave mixing. The mixing frequency difference (lambda1 lambda2 - lambda3) has the advantage of mixing the sum frequency because phase matching can provide greater tuning. In particular, the two-photon mixing frequency difference from an ArF (193Ã, nm) eczema laser with visible laser or close to IR in hydrogen or krypton provides an enhanced and improved tunable VUV from 100 nm to 200 nm. Practically, the lack of suitable gas/vapor cell windows over the limit of the lithium fluoride wavelength limits the tuning range longer than about 110 nm. The tunable VUV wavelength of up to 75 nm is achieved using the free-window configuration.
The extreme UV plasma and synchrotron sources
Lasers have been used to indirectly produce non-coherent UV (EUV) radiation at 13.5 nm for extreme ultraviolet lithography. EUV is not emitted by lasers, but rather by electron transitions in very hot tin or xenon plasma, attracted by excimer lasers. This technique does not require synchrotron, but can produce UV on the edge of the X-ray spectrum. Synchrotron light sources can also produce all UV wavelengths, including those in the UV and X-ray spectral limits at 10 nm.
The impact of ultraviolet radiation on human health has implications for the risks and benefits of sun exposure and is also involved in issues such as fluorescent lighting and health. Too much exposure to sunlight can be harmful, but in moderation, sun exposure is beneficial.
Favorable effect
"There is no doubt that a little sunshine is good for you! But 5 to 15 minutes of casual sun exposure from the hands, face and arms two to three times a week during the summer is enough to keep your vitamin D levels high. - World Health Organization
UV light causes the body to produce vitamin D, which is essential for life. The human body needs UV radiation so that one can maintain adequate levels of vitamin D; however, excessive exposure produces harmful effects that typically outweigh the benefits.
Vitamin D promotes the creation of serotonin. The production of serotonin is in direct proportion to the level of sunlight received by the body. Serotonin is considered to give the sensation of happiness, prosperity and tranquility for humans.
Skin condition
UV rays also treat certain skin conditions. Modern phototherapy has been used to successfully treat psoriasis, eczema, jaundice, vitiligo, atopic dermatitis, and local scleroderma. In addition, UV rays, especially UVB radiation, have been shown to induce cell cycle capture in keratinocytes, the most common type of skin cell. Thus, sunlight therapy can be a candidate for the treatment of conditions such as psoriasis and exfoliative cheilitis, a condition in which skin cells divide faster than normal or required.
Malicious effects
In humans, excessive exposure to UV radiation can result in acute and chronic adverse effects on the dioptric system of the eye and the retina. The risks are rising at high altitudes and people living in high latitudes where snow cover the soil right into early summer and the position of the sun even at its low peak is very risky. Skin, circadian, and immune system can also be affected.
The differential effects of different wavelengths of light on the human cornea and skin are sometimes called "spectrum of erythemal actions." The action spectrum shows that UVA does not cause immediate reaction, but UV starts to cause photoceratitis and skin redness (with more sensitive Caucasian) at wavelengths that begin near the beginning of the UVB band at 315 nm, and rapidly increase 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 shorter UV wavelengths, damage continues, but the bright effect is not so great with so little penetrating the atmosphere. The WHO standard ultraviolet index is a widely published measurement of the total UV wavelength that causes skin to burn on human skin, by exposing UV light to the effects of the action spectrum at specific times and locations. This standard shows that most of the sunburn occurs due to UV at wavelengths near the UVA and UVB borders. Bioolympics finds the UV reaction index to detect UV leakage.
Skin damage
Overexposure to UVB radiation can not only cause skin burn but also some forms of skin cancer. However, redness and eye irritation (which are mostly not caused by UVA) do not predict long-term effects of UV, although they reflect direct damage to DNA by ultraviolet.
All UV radiation bands damage collagen fibers and accelerate skin aging. Both UVA and UVB destroy vitamin A in the skin, which can lead to further damage.
UVB radiation can cause direct DNA damage. This cancer connection is one of the reasons for concerns about ozone depletion and ozone holes.
The most deadly type of skin cancer, malignant melanoma, is largely due to DNA damage independent of UVA radiation. This can be seen from the absence of direct UV signature mutations in 92% of all melanomas. Sometimes overexposure and sunburn may be a greater risk factor for melanoma than moderate long-term exposure. UVC is the highest and most dangerous type of ultraviolet radiation, and causes adverse effects that can be mutagenic or carcinogenic.
In the past, UVA was considered harmless or less harmful than UVB, but today it is known to contribute to skin cancer through indirect DNA damage (free radicals such as reactive oxygen species). UVA can produce highly reactive chemical intermediates, such as hydroxyl and oxygen radicals, which in turn can damage DNA. The indirect DNA damage caused by UVA mostly consists of single-strand damage in DNA, whereas UVB-induced damage includes the direct formation of thymine dimers or other pyrimidine dimers and double-stranded DNA damage. UVA is immunosuppressive for the whole body (accounting for most of the immunosuppressive effects of sun exposure), and is mutagenic for basal cell keratinocytes on the skin.
UVB photons can cause direct DNA damage. UVB radiation excites DNA molecules in skin cells, causing covalent straying to form between adjacent pyrimidine bases, resulting in dimers. Most UV-induced pyrimidine dimers in DNA are removed by a process known as nucleotide excision repair that employs about 30 different proteins. The pyrimidine dimension that escapes this repair process can lead to programmed cell death (apoptosis) or it can lead to DNA replication errors that cause mutations.
As a defense against UV radiation, the amount of chocolate pigment melanin in the skin increases when exposed to moderate levels (depending on skin type) radiation; This is commonly known as sun tan. The goal of melanin is to absorb UV radiation and dispose of energy as harmless heat, protecting the skin from direct and indirect DNA damage from UV. UVA provides a rapid tan that lasts for days by oxidizing the existing melanin and triggering melanin release from melanocytes. UVB produces a tan that takes about 2 days to develop because it stimulates the body to produce more melanin.
Sunscreen security debate
Medical organizations recommend that patients protect themselves from UV radiation by using sunscreen. Five sunscreen ingredients have been shown to protect mice from skin tumors. However, some sunscreen chemicals produce potentially harmful substances when illuminated when 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.
Sunscreens reduce direct DNA damage that causes sunburn, by blocking UVB, and the regular SPF rating indicates how effective this radiation is blocked. SPF, therefore, is also called UVB-PF, for "UVB protection factor". This rating, however, does not offer data on important UVA protection, which does not primarily cause sunburn but is still dangerous, as it causes indirect DNA damage and is also considered carcinogenic. Some studies show that the absence of UVA filters may be the cause of the high incidence of melanoma found in sunscreen users compared to non-users. Some sunscreen lotions now contain compounds including titanium dioxide, zinc oxide and avobenzone that help protect against UVA rays.
The photochemical properties of melanin make it a very good photoprotektan. However, sunscreen chemicals can not remove energy from the excited state as efficiently as melanin and therefore, if the sunscreen material penetrates into the lower layers of the skin, the number of reactive oxygen species can be increased. The amount of sunscreen that penetrates through the stratum corneum may or may not be large enough to cause damage.
In an experiment by Hanson et al. published in 2006, the number of harmful reactive oxygen species (ROS) measured on untreated skin and sun exposed skin. In the first 20 minutes, sunscreen films have a protective effect and the number of ROS species is smaller. However, after 60 minutes, the amount of sunscreen absorbed is so high that the amount of ROS is higher in sunlight treated skin than on untreated skin. This study shows that sunscreen should be re-applied within 2 hours to prevent UV rays from penetrating into living sun-lined skin cells.
Agravation of certain skin conditions
Ultraviolet radiation can worsen some skin conditions and diseases, including systemic lupus erythematosus, SjÃÆ'¶gren syndrome, Sinear Usher syndrome, rosacea, dermatomyositis, Dier's disease, and Kindler-Weary syndrome.
Eye damage
The most sensitive eye to UV damage in the UVC band is lower at 265-275 nm. This wavelength radiation is virtually absent from sunlight but is found in arc welders and other artificial sources. This exposure can cause "lightning welder" or "bow eye" (photokeratitis) and can cause cataract, pterygium and pinguecula formation. For lower levels, UVB rays in the sun from 310-280 nm also cause fotokeratitis ("snow blindness"), and the cornea, lens, and retina can be damaged.
Protective goggles are beneficial for those affected by ultraviolet radiation. Because light can reach the eyes from the sides, full-coverage eye protection is usually necessary if there is an increased risk of exposure, such as on mountain altitudes. Mountain climbers are exposed to higher levels of UV radiation than usual, both because there is less atmospheric filtering and because of the reflection of snow and ice. Ordinary glasses that are not treated provide protection. Most plastic lenses provide more protection than glass lenses, because, as mentioned above, transparent glass against UVA and common acrylic plastic used for less lenses. Some plastic lens materials, such as polycarbonate, inherently block most UV.
Degradation of polymers, pigments and dyes
Ultraviolet degradation is one form of polymer degradation that affects plastic exposed to sunlight. The problem arises as a change of color or fading, cracking, loss of strength or disintegration. The effect of the attack increases with the time of daylight and the intensity of sunlight. The addition of UV absorber inhibits its effect.
Sensitive polymers include thermoplastics and specialty fibers such as aramid. UV absorption leads to chain degradation and loss of power at sensitive points in the chain structure. Aramid ropes should be protected with thermoplastic sheath if they want to maintain their strength.
Many pigments and dyes absorb UV and change color, so painting and textiles may require extra protection from both sunlight and fluorescent light, two sources of UV radiation. Glass windows absorb some harmful UV, but valuable artifacts require extra protection. Many museums put black curtains on top of watercolors and ancient textiles, for example. Since watercolors can have very low pigment levels, they require extra protection from UV. Various forms of image framing, including acrylic (plexiglass), laminate, and coating, offer different levels of UV protection (and visible light).
Apps
Because of its ability to cause chemical reactions and excite fluorescence in materials, ultraviolet radiation has a number of applications. The following table provides some use of specific wavelength bands in the UV spectrum
- 13.5Ã, nm : Extreme ultraviolet lithography
- 30-200Ã, nm : photoionization, ultraviolet photoelectron spectroscopy, manufacture of standard integrated circuits with photolithography
- 230-365Ã, nm : UV-ID, label tracking, barcode
- 230-400Ã, nm : Optical sensor, various instrumentation
- 240-280Ã, nm : Disinfection, surface and water decontamination (DNA absorption has a peak at 260 nm)
- 200-400Ã ¢ â,¬ : Forensic analysis, drug detection
- 270-360Ã, nm : Protein analysis, DNA sequencing, drug discovery
- 280-400Ã, nm : Cell medical imaging
- 300-320Ã, nm : Light therapy in medicine
- 300-365Ã, nm : Healing polymer and printer ink
- 350-370Ã, nm : Bug zappers (flies most interested in light at 365Ã, nm)
Photography
Photographic films respond to ultraviolet radiation but camera glass lenses usually block radiation shorter than 350Ã, nm. A slightly yellow UV-blocking filter is often used for outdoor photography to prevent unwanted bluing and over-exposure by UV light. For photography near UV, special filters can be used. Photography with wavelengths shorter than 350 m requires special quartz lenses that do not absorb radiation. The digital camera sensor may have an internal filter blocking the UV to improve the color rendition accuracy. Sometimes these internal filters can be removed, or may not exist, and external visible light filters set up the camera for near-UV photography. Some cameras are designed for use in UV.
Photography by reflecting ultraviolet radiation is useful for medical, scientific, and forensic investigations, in widespread applications such as detecting skin bruising, document change, or painting restoration work. Fluorescence photography produced by ultraviolet illumination uses visible wavelengths of light.
In ultraviolet astronomy, measurements are used to look at the chemical composition of the interstellar medium, as well as the temperature and composition of the star. Because the ozone layer blocks many UV frequencies from reaching the telescope on the Earth's surface, most UV observations are made from outer space.
Electrical and electronic industry
Corona discharge on electrical equipment can be detected by its ultraviolet emission. Corona leads to degradation of electrical insulation and emission of ozone and nitrous oxide.
EPROM (Deleted Read-Only Programmable Memory) is removed by exposure to UV radiation. These modules have a transparent (quartz) window at the top of the chip that allows UV radiation at.
Use of fluorescent dye
Colorless colored fluorescents emitting blue light under UV are added as optical brightener on paper and fabric. The blue light emitted by these agents counteracts the possible yellow color and causes the colors and whites to appear whiter or more brightly colored.
UV fluorescent dyes that glow in primary colors are used in paints, paper and textiles either to enhance the color under daylight lighting or to give special effects when illuminated with UV lamps. Blacklight paint that contains dye that shines under UV is used in a number of art and aesthetic applications.
To help prevent currency counterfeiting, or forgery of important documents such as driver's licenses and passports, the paper may include a UV sign or a fluorescent multicolor fiber visible under ultraviolet light. Stamps are marked with phosphors that shine under UV light to allow automatic detection of the stamp and face the letter.
UV fluid dyes are used in many applications (eg, biochemistry and forensics). Some brands of pepper spray will leave the invisible chemicals (UV dyes) that are not easy to clean on a pepper-sprayed attacker, which will help the police identify the attacker later.
In some types of nondestructive tests UV stimulates fluorescent dyes to highlight defects in various materials. These dyes can be brought to surface breaking defects by capillary action (liquid penetrating inspection) or they may be attached to ferrite particles caught in the field of magnetic leaks in iron (examination of magnetic particles).
Analytics usage
Forensics
UV is an investigative tool at the crime scene helping in finding and identifying body fluids such as semen, blood, and saliva. For example, ejaculatory fluid or saliva can be detected by a high-power UV source, regardless of the structure or color of the surface of the deposited liquid. UV-Vis microspectroscopy is also used to analyze trace evidence, such as textile fibers and paint chips, as well as documents in question.
Other apps include various authentication collections and art, and detect counterfeit currency. Even materials that are not specifically marked with sensitive UV dyes may have exceptional fluorescence under UV exposure or can fluoresce differently under shortwave versus long wavelength ultraviolet.
Increase ink contrast
Using multi-spectral imagery it is possible to read unreadable papyrus, such as the burning papyrus of the Papyrus Villa or Oxyrhynchus, or Archimedes palimpsest. This technique involves taking pictures of unread documents using different filters in the infrared or ultraviolet range, tuned to capture specific wavelengths of light. Thus, the optimal spectral portion can be found to distinguish the ink from the paper on the surface of the papyrus.
A simple NUV source can be used to highlight ferrous, iron-based ink on vellum.
Sanitation compliance
Ultraviolet aid in detecting deposits of organic matter that remain on the surface where periodic cleaning and sanitation may not be done properly. It is used in hotel, manufacturing, and other industries where the level of cleanliness or contamination is checked.
The timeless news feature for many television news organizations involves investigative reporters using similar devices to uncover unsanitary conditions in hotels, public toilets, hand rails, and the like.
Chemistry
UV/VIS spectroscopy is widely used as a technique in chemistry to analyze chemical structure, the most important being the conjugated system. UV radiation is often used to stimulate a given sample in which fluorescent emissions are measured with a spectrofluorometer. In biological research, UV radiation is used for the quantification of nucleic acids or proteins.
Ultraviolet light is also used in analyzing minerals and gems.
In pollution control applications, ultraviolet analyzers are used to detect nitrogen oxide emissions, sulfur compounds, mercury, and ammonia, for example in the flue gas of a fossil fuel power plant. Ultraviolet radiation can detect the thinness of spilled oil in water, either by the high reflectivity of the oil film at UV wavelength, fluorescence of compounds in oil or by absorbing UV created by Raman scattering in water.
Materials science using
Fire detection
In general, ultraviolet detectors use solid-state devices, such as those based on silicon carbide or aluminum nitride, or gas-filled tubes as sensing elements. UV sensors that are sensitive to UV in any part of the spectrum respond to radiation by sunlight and artificial light. The burning hydrogen fire, for example, radiates strongly in the range of 185 to 260 nanometers and is only very weak in the IR region, whereas coal fires emit very weakly in the UV band but are very strong at IR wavelengths; thus, fire detectors that operate using UV and IR detectors are more reliable than UV detectors only. Almost all fires emit radiation in the UVC band, while the solar radiation in the band is absorbed by Earth's atmosphere. The result is that the UV detector is "blind sun", which means it will not cause 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 hydrocarbons, metals, sulfur, hydrogen, hydrazine, and ammonia. Arc welding, electric arcs, lightning, X-rays are used in nondestructive metal testing equipment (though this is highly unlikely), and radioactive materials can produce levels that will activate the UV detection system. The presence of UV absorbent gases and vapors will weaken UV radiation from fire, affecting the detector's ability to detect fire. Likewise, the presence of oil mist in air or oil film on the detector window will have the same effect.
Photolithography
Ultraviolet radiation is used for very fine resolution photolithography, a procedure in which a chemical called photoresist is exposed to UV radiation that has passed through the mask. Exposure causes a chemical reaction to occur in the photoresist. After the removal of undesirable photoreses, the pattern determined by the mask remains in the sample. The later steps can be taken to "etch" away, deposit or modify the sample area where there is no fixed photoresist.
Photolithography is used in the manufacture of semiconductors, integrated circuit components, and printed circuit boards. The photolithography process used to make electronic integrated circuits today uses 193Ã, nm UV and experimentally uses 13.5Ã, nm UV for extreme ultraviolet lithography.
Polymers
Electronic components that require clear transparency for incoming or outgoing light (panels and photovoltaic sensors) can be installed using acrylic resins that are cured using UV energy. The advantage is low and dry VOC emissions.
Specific inks, coatings, and adhesives are formulated with photo and resin makers. When exposed to UV rays, polymerization occurs, so the adhesive hardens or heals, usually within a few seconds. Applications include glass and plastic bonding, optical fiber coatings, floor layers, UV coating and finished papers in offset printing, dental fillings, and decorative "gel" nails.
UV sources for UV curing applications include UV lights, UV LEDs, and Excimer flash lights. Fast processes such as flexo printing or offset printing require high-intensity focused light through the reflector to the medium and moving substrates so that high-pressure Hg (mercury) or Fe (iron, doped) -bigbig is used, energized with electric arcs or microwaves. Low power fluorescent lamps and LEDs can be used for static applications. Small high-pressure lamps can have a focus of light and are transmitted to the work area through a light guide containing liquids or optical fibers.
The UV impact on polymers is used for polymer surface (roughness and hydrophobic) modification. For example, the surface of poly (methyl methacrylate) can be smoothed with ultraviolet vacuum.
UV radiation is useful in preparing low surface energy polymers for adhesives. UV-exposed polymers oxidize, thereby increasing the polymer surface energy. Once the polymer surface energy has increased, the bond between the adhesive and the polymer is stronger.
Air purification
Using the catalytic chemical reaction of titanium dioxide and UVC exposure, the oxidation of organic matter converts pathogens, pollen, and mold spores into innocuous byproducts. The UV cleaning mechanism is a photochemical process. Contaminants in indoor environments are almost entirely carbon-based organic compounds, which are damaged when exposed to high-intensity UV at 240 to 280 nm. Shortwave ultraviolet radiation can destroy DNA in living microorganisms. The effectiveness of UVC is directly related to the intensity and time of exposure.
UV has also been shown to reduce gas contaminants such as carbon monoxide and VOC. UV lights radiating at 184 and 254 nm can remove low concentrations of hydrocarbons and carbon monoxide if air is recycled between the room and the lamp room. This arrangement prevents the entry of ozone into the treated air. Likewise, air can be handled by passing by a single UV source that operates at 184 nm and passes through iron pentaoxide to remove ozone generated by UV lamps.
Sterilization and disinfection
Ultraviolet lights are used to sterilize workspaces and equipment used in biological laboratories and medical facilities. The commercially available low-pressure mercury vapor lamp emits about 86% of their radiation at 254 nanometers (nm), with 265 nm being the peak genetic effectiveness curve. UV at this wavelength destroys the DNA of the microorganism so it can not reproduce, making it harmless, (although organisms can not be killed). Because microorganisms can be protected from ultraviolet light in small cracks and other shaded areas, these lights are only used as supplements for other sterilization techniques.
UV-C LEDs are relatively new to the commercial market and are gaining in popularity. Due to their monochromatic properties (Â ± 5nm) these LEDs can target certain wavelengths required for disinfection. This is especially important because it recognizes that pathogens vary in sensitivity to specific UV wavelengths. LEDs are mercury-free, instant on/off, and have unlimited cycles throughout the day.
Disinfection using UV radiation is commonly used in wastewater treatment applications and finds increased use in municipal drinking water treatment. Many bottling springs use UV disinfection equipment to sterilize their water. Solar water disinfection has been studied for the treatment of contaminated low-cost water using natural sunlight. UV-A irradiation and increased water temperatures kill organisms in the water.
Ultraviolet radiation is used in some food processes to kill unwanted microorganisms. UV can be used to pasteurize fruit juices by draining the juice to a high-intensity ultraviolet source. The effectiveness of such a process depends on the absorption of UV from the juice.
Pulsed light (PL) is a technique of killing microorganisms on surfaces using pulses from a wide broad spectrum, rich in UV-C between 200 and 280 nm. The throbbing light works with xenon flash lights that can generate lightning several times per second. Robot disinfection using pulsed UV
Biological
Some animals, including birds, reptiles, and insects like bees, can see near ultraviolet waves. Many fruits, flowers, and seeds stand out from the background of ultraviolet waves compared to human color vision. Scorpions shine or take yellow to green under UV light, thus helping to control this arachnid. Many birds have patterns in their fur that are not visible at ordinary wavelengths but can be observed in ultraviolet, and the urine and other secretions of some animals, including dogs, cats, and humans, are much more easily recognizable by ultraviolet. Rat urine pathways can be detected by pest control technicians for proper treatment for full residences.
Butterflies use ultraviolet as a communication system for the introduction of sex and mating behavior. For example, in the butterfly Colias eurytheme , men rely on visual cues to search for and identify women. Instead of using chemical stimuli to find a partner, men are attracted by the ultraviolet color that reflects women's rear wing. In the Pieris prisoner the butterfly shows that women in northern Finland with UV radiation in the environment have stronger UV signals to attract their males than those further south. This suggests that it is evolutionally more difficult to increase UV sensitivity from the eyes of men than to increase the UV signals emitted by women.
Many insects use ultraviolet wavelength emission from celestial bodies as a reference for flight navigation. Local ultraviolet transmitters will usually interfere with the navigation process and will eventually attract flying insects.
Green fluorescent protein (GFP) is often used in genetics as a marker. Many substances, such as proteins, have significant light absorption bands in the ultraviolet that are attractive in biochemistry and related fields. UV light spectrophotometers are common in such laboratories.
An ultraviolet trap called a bug zappers is used to remove various small flying insects. They are attracted to UV and killed by electric shock, or trapped once they come into contact with the device. Different designs of ultraviolet radiation traps are also used by entomologists to collect nocturnal insects during a survey of faunistic surveys.
Therapy
Ultraviolet radiation is very helpful in the treatment of skin conditions such as psoriasis and vitiligo. UVA exposure, while hyper-photosensitive skin, by taking psoralens is an effective treatment for psoriasis. Because of the potential for psoralen to cause damage to the liver, PUVA therapy can only be used in limited quantities during the lifetime of the patient.
UVB phototherapy does not require additional drugs or topical preparations for therapeutic benefits; only exposure required. 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
Reptiles require UVB for vitamin D biosynthesis, and other metabolic processes. Special cholecalciferol (vitamin D3), which is necessary for cellular/neural function as well as the utilization of calcium for bone and egg production. UVA wavelengths are also seen by many reptiles and may play an important role in their ability to survive in the wild as well as visual communication between individuals. Therefore, in typical reptile enclosures, UV/b fluorescent sources (at appropriate strength/spectrum for species), should be available for many species of prisoners to survive. Simple supplementation with cholecalciferol (Vitamin D3) will not be enough because there is a complete "leapfrogged" biosynthetic pathway (the risk of possible overdose), intermediate molecules and metabolites also place important functions in animal health. Natural sunshine at the right level will always be superior to artificial sources, but this is possible for carers in different parts of the world.
It is a known problem that high levels of output from the UVA spectrum can cause cell and DNA damage to their sensitive parts of the body - especially blind eyes are the result of inappropriate use of UVA/b sources and photoceratitis placement.. For many guards there must also be supplies for an adequate heat source that has resulted in hot marketing and a mild "combination" product. Guards should exercise caution against the combination of 'light/heat and UVA/b generators, they typically emit high levels of UVa with lower defined UVB levels and are difficult to control so that animals can meet their needs. A better strategy is to use the individual sources of these elements and so that they can be placed and controlled by the guards for maximum benefit from the animals.
Evolutionary meaning
Source of the article : Wikipedia
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