Because of its ability to cause chemical reactions and excite fluorescence in materials,<unk>  radiation has a number of applications. The following table gives some uses of specific wavelength bands in the<unk>  spectrum *13.5 nm: Extreme<unk>  lithography *30–200 nm: Photoionization,<unk>  photoelectron spectroscopy, standard integrated circuit manufacture by photolithography *230–365 nm:<unk> -ID, label tracking, barcodes *230–400 nm: Optical sensors, various instrumentation *240–280 nm: Disinfection, decontamination of surfaces and water (DNA absorption has a peak at 260 nm), germicidal lamps *200–400 nm: Forensic analysis, drug detection *270–360 nm: Protein analysis, DNA sequencing, drug discovery *280–400 nm: Medical imaging of cells *300–320 nm: Light therapy in medicine *300–365 nm: Curing of polymers and printer inks *350–370 nm: Bug zappers (flies are most attracted to light at 365 nm) Photography A portrait taken using only<unk>  light between the wavelengths of 335 and 365 nanometers. Photographic film responds to<unk>  radiation but the glass lenses of cameras usually block radiation shorter than 350 nm. Slightly yellow<unk> -blocking filters are often used for outdoor photography to prevent unwanted bluing and overexposure by<unk>  rays. For photography in the near<unk> , special filters may be used. Photography with wavelengths shorter than 350 nm requires special quartz lenses which do not absorb the radiation. Digital cameras sensors may have internal filters that block<unk>  to improve color rendition accuracy. Sometimes these internal filters can be removed, or they may be absent, and an external visible-light filter prepares the camera for near-UV photography. A few cameras are designed for use in the<unk> . Photography by reflected<unk>  radiation is useful for medical, scientific, and forensic investigations, in applications as widespread as detecting bruising of skin, alterations of documents, or restoration work on paintings. Photography of the fluorescence produced by<unk>  illumination uses visible wavelengths of light. Aurora at Jupiter's north pole as seen in<unk>  light by the Hubble Space Telescope. In<unk>  astronomy, measurements are used to discern the chemical composition of the interstellar medium, and the temperature and composition of stars. Because the ozone layer blocks many<unk>  frequencies from reaching telescopes on the surface of the Earth, most<unk>  observations are made from space. Electrical and electronics industry Corona discharge on electrical apparatus can be detected by its<unk>  emissions. Corona causes degradation of electrical insulation and emission of ozone and nitrogen oxide. EPROMs (Erasable Programmable Read-Only Memory) are erased by exposure to<unk>  radiation. These modules have a transparent (quartz) window on the top of the chip that allows the<unk>  radiation in. Fluorescent dye uses Colorless fluorescent dyes that emit blue light under<unk>  are added as optical brighteners to paper and fabrics. The blue light emitted by these agents counteracts yellow tints that may be present and causes the colors and whites to appear whiter or more brightly colored.<unk>  fluorescent dyes that glow in the primary colors are used in paints, papers, and textiles either to enhance color under daylight illumination or to provide special effects when lit with<unk>  lamps. Blacklight paints that contain dyes that glow under<unk>  are used in a number of art and aesthetic applications. Amusement parks often use<unk>  lighting to fluoresce ride artwork and backdrops. This often has the side effect of causing rider's white clothing to glow light-purple. A bird appears on many Visa credit cards when they are held under a<unk>  light source To help prevent counterfeiting of currency, or forgery of important documents such as driver's licenses and passports, the paper may include a<unk>  watermark or fluorescent multicolor fibers that are visible under<unk>  light. Postage stamps are tagged with a phosphor that glows under<unk>  rays to permit automatic detection of the stamp and facing of the letter.<unk>  fluorescent dyes are used in many applications (for example, biochemistry and forensics). Some brands of pepper spray will leave an invisible chemical <unk>  dye) that is not easily washed off on a pepper-sprayed attacker, which would help police identify the attacker later. In some types of nondestructive testing<unk>  stimulates fluorescent dyes to highlight defects in a broad range of materials. These dyes may be carried into surface-breaking defects by capillary action (liquid penetrant inspection) or they may be bound to ferrite particles caught in magnetic leakage fields in ferrous materials (magnetic particle inspection). Analytic uses Forensics<unk>  is an investigative tool at the crime scene helpful in locating and identifying bodily fluids such as semen, blood, and saliva. For example, ejaculated fluids or saliva can be detected by high-power<unk>  sources, irrespective of the structure or colour of the surface the fluid is deposited upon.<unk> –vis microspectroscopy is also used to analyze trace evidence, such as textile fibers and paint chips, as well as questioned documents. Other applications include the authentication of various collectibles and art, and detecting counterfeit currency. Even materials not specially marked with<unk>  sensitive dyes may have distinctive fluorescence under<unk>  exposure or may fluoresce differently under short-wave versus long-wave<unk> . Enhancing contrast of ink Using multi-spectral imaging it is possible to read illegible papyrus, such as the burned papyri of the Villa of the Papyri or of Oxyrhynchus, or the Archimedes palimpsest. The technique involves taking pictures of the illegible document using different filters in the infrared or<unk>  range, finely tuned to capture certain wavelengths of light. Thus, the optimum spectral portion can be found for distinguishing ink from paper on the papyrus surface. Simple NUV sources can be used to highlight faded iron-based ink on vellum. Sanitary compliance After a training exercise involving fake body fluids, a healthcare worker's personal protective equipment is checked with<unk>  light to find invisible drops of fluids. These fluids could contain deadly viruses or other contamination.<unk>  light helps detect organic material deposits that remain on surfaces where periodic cleaning and sanitizing may have failed. It is used in the hotel industry, manufacturing, and other industries where levels of cleanliness or contamination are inspected. Perennial news features for many television news organizations involve an investigative reporter using a similar device to reveal unsanitary conditions in hotels, public toilets, hand rails, and such. Chemistry<unk> /Vis spectroscopy is widely used as a technique in chemistry to analyze chemical structure, the most notable one being conjugated systems.<unk>  radiation is often used to excite a given sample where the fluorescent emission is measured with a spectrofluorometer. In biological research,<unk>  radiation is used for quantification of nucleic acids or proteins. In environmental chemistry,<unk>  radiation could also be used to detect Contaminants of emerging concern in water samples. In pollution control applications,<unk>  analyzers are used to detect emissions of nitrogen oxides, sulfur compounds, mercury, and ammonia, for example in the flue gas of fossil-fired power plants.<unk>  radiation can detect thin sheens of spilled oil on water, either by the high reflectivity of oil films at<unk>  wavelengths, fluorescence of compounds in oil, or by absorbing of<unk>  created by Raman scattering in water. A collection of mineral samples brilliantly fluorescing at various wavelengths as seen while being irradiated by<unk>  light.<unk>  lamps are also used as part of the analysis of some minerals and gems. Material science uses Fire detection In general,<unk>  detectors use either a solid-state device, such as one based on silicon carbide or aluminium nitride, or a gas-filled tube as the sensing element.<unk>  detectors that are sensitive to<unk>  in any part of the spectrum respond to irradiation by sunlight and artificial light. A burning hydrogen flame, for instance, radiates strongly in the 185- to 260-nanometer range and only very weakly in the IR region, whereas a coal fire emits very weakly in the<unk>  band yet very strongly at IR wavelengths; thus, a fire detector that operates using both<unk>  and IR detectors is more reliable than one with a<unk>  detector alone. Virtually all fires emit some radiation in the<unk> C band, whereas the Sun's radiation at this band is absorbed by the Earth's atmosphere. The result is that the<unk>  detector is "solar blind", meaning it will not cause an alarm in response to radiation from the Sun, so it can easily be used both indoors and outdoors.<unk>  detectors are sensitive to most fires, including hydrocarbons, metals, sulfur, hydrogen, hydrazine, and ammonia. Arc welding, electrical arcs, lightning, X-rays used in nondestructive metal testing equipment (though this is highly unlikely), and radioactive materials can produce levels that will activate a<unk>  detection system. The presence of<unk> -absorbing gases and vapors will attenuate the<unk>  radiation from a fire, adversely affecting the ability of the detector to detect flames. Likewise, the presence of an oil mist in the air or an oil film on the detector window will have the same effect. Photolithography<unk>  radiation is used for very fine resolution photolithography, a procedure wherein a chemical called a photoresist is exposed to<unk>  radiation that has passed through a mask. The exposure causes chemical reactions to occur in the photoresist. After removal of unwanted
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