Ultraviolet (UV) light is electromagnetic radiation Electromagnetic radiation is a phenomenon that takes the form of self-propagating waves in a vacuum or in matter. It comprises electric and magnetic field components, which oscillate in phase perpendicular to each other and perpendicular to the direction of energy propagation. Electromagnetic radiation is classified into several types according to with a wavelength In physics, the wavelength of a sinusoidal wave is the spatial period of the wave – the distance over which the wave's shape repeats. It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a characteristic of both traveling waves and shorter than that of visible light The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light. A typical human eye will respond to wavelengths from about 390 to 750 nm. In terms of frequency, this corresponds to a band in the vicinity of 400-790, but longer than x-rays X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz (3 × 1016 Hz to 3 × 1019 Hz) and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma rays. In many, in the range 10 nm A nanometre (Ancient Greek: νάνος, nanos, "dwarf"; μέτρον, metrοn, "unit of measurement") is a unit of length in the metric system, equal to one billionth of a metre to 400 nm, and energies from 3eV In physics, the electron volt is a unit of energy equal to approximately 1.602×10−19 J. By definition, it is equal to the amount of kinetic energy gained by a single unbound electron when it accelerates through an electric potential difference of one volt. Thus it is 1 volt (1 joule per coulomb) multiplied by the electron charge (1 e, or 1.60217 to 124 eV. It is so named because the spectrum consists of electromagnetic waves with frequencies higher than those that humans Humans, known taxonomically as Homo sapiens , are the only living species in the Homo genus of bipedal primates in Hominidae, the great ape family. However, in some cases "human" is used to refer to any member of the genus Homo identify as the colour violet As the name of a color, violet is used in two senses: first, referring to the color of light at the short-wavelength end of the visible spectrum, approximately 380–420 nm when indigo is recognized as a distinct color, or more commonly 380–450 nm (this is a spectral color). Second, violet may refer to a shade of purple, that is, a mixture of.
UV light is found in sunlight Sunlight, in the broad sense, is the total frequency spectrum of electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the Earth's atmosphere, and solar radiation is obvious as daylight when the Sun is above the horizon and is emitted by electric arcs An electric arc is an electrical breakdown of a gas which produces an ongoing plasma discharge, resulting from a current flowing through normally nonconductive media such as air. A synonym is arc discharge. The phenomenon was first described by Vasily V. Petrov, a Russian scientist who discovered it in 1802. An archaic term is voltaic arc as used and specialized lights such as black lights A "black light" or "UV light" is a lamp emitting electromagnetic radiation that is almost exclusively in the soft near ultraviolet range, and emits very little visible light. In medicine, forensics, and some other scientific fields, such a light source is referred to as a Wood's lamp. Classified as non-ionizing radiation Non-ionizing radiation or non-ionising radiation refers to any type of electromagnetic radiation that does not carry enough energy per quantum to ionize atoms or molecules — that is, to completely remove an electron from an atom or molecule. Instead of producing charged ions when passing through matter, the electromagnetic radiation has, it can cause chemical reactions, and causes many substances to glow or fluoresce Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation of a different wavelength. In most cases, emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation. However, when the absorbed electromagnetic radiation is intense, it is possible for one electron to. Most people are aware of the effects of UV through the painful condition of sunburn A sunburn is a burn to living tissue, such as skin, which is produced by overexposure to ultraviolet radiation, commonly from the sun's rays. Usual mild symptoms in humans and animals include red or reddish skin that is hot to the touch, general fatigue, and mild dizziness. An excess of UV radiation can be life-threatening in extreme cases, but the UV spectrum has many other effects, both beneficial and damaging, to human health.
Discovery
The discovery of UV radiation was intimately associated with the observation that silver salts A silver halide is one of the compounds formed between silver and one of the halogens — silver bromide , chloride (AgCl), iodide (AgI), and three forms of silver fluorides. As a group, they are often referred to as the silver halides, and are often given the pseudo-chemical notation AgX. Although most silver halides involve silver atoms with darken when exposed to sunlight. In 1801 the German physicist Johann Wilhelm Ritter Johann Wilhelm Ritter was a German chemist and physicist. He was born in Samitz bei Haynau, Silesia (now Chojnów, Poland) made the hallmark observation that invisible rays just beyond the violet end of the visible spectrum were especially effective at darkening silver chloride Silver chloride is a chemical compound with the chemical formula Ag -soaked paper. He called them "de-oxidizing rays" to emphasize chemical reactivity Reactivity is a somewhat vague concept used in chemistry which appears to embody both kinetic and thermodynamic factors. For example, it is commonly asserted that 'the reactivity of group one metals increases down the group in the periodic table, or that hydrogen's reactivity is evidenced by its reaction with oxygen. In fact, the rate of reaction and to distinguish them from "heat rays" at the other end of the visible spectrum. The simpler term "chemical rays" was adopted shortly thereafter, and it remained popular throughout the 19th century. The terms chemical and heat rays were eventually dropped in favor of ultraviolet and infrared Infrared light is electromagnetic radiation with a wavelength between 0.7 and 300 micrometres, which equates to a frequency range between approximately 1 and 430 THz radiation In physics, radiation describes a process in which energetic particles or waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing. The word radiation is commonly used in reference to ionizing radiation only , but it may also refer to non-ionizing radiation (e.g., radio waves or visible light), respectively.[1]
The discovery of the ultraviolet radiation below 200 nm, named vacuum ultraviolet because it is strongly absorbed by air, was made in 1893 by the German physicist Victor Schumann.[2]
Origin of the term
The name means "beyond violet" (from Latin Latin or sometimes Roman is an Italic language originally spoken in Latium and Ancient Rome. Although often considered a dead language, in view of the fact that it has no native speakers, a small number of scholars can fluently speak it and it continues to be taught in schools and universities and has been, and currently is, used in the process of ultra, "beyond"), violet being the color Color or colour is the visual perceptual property corresponding in humans to the categories called red, green, blue and others. Color derives from the spectrum of light (distribution of light energy versus wavelength) interacting in the eye with the spectral sensitivities of the light receptors. Color categories and physical specifications of of the shortest wavelengths of visible light. UV light has a shorter wavelength than that of violet light.
Subtypes
The electromagnetic spectrum of ultraviolet light can be subdivided in a number of ways. The draft ISO standard on determining solar irradiances (ISO-DIS-21348)[3] describes the following ranges:
In photolithography Photolithography is a process used in microfabrication to selectively remove parts of a thin film or the bulk of a substrate. It uses light to transfer a geometric pattern from a photo mask to a light-sensitive chemical photo resist, or simply "resist," on the substrate. A series of chemical treatments then engraves the exposure pattern and laser Light Amplification by Stimulated Emission of Radiation is a mechanism for emitting electromagnetic radiation, often visible light, via the process of stimulated emission. The emitted laser light is (usually) a spatially coherent, narrow low-divergence beam, that can be manipulated with lenses. In laser technology, "coherent light" technology, the term deep ultraviolet or DUV refers to wavelengths below 300 nm. "Vacuum UV" is so named because it is absorbed strongly by air The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night. Dry air contains roughly (by volume) 78.09% nitrogen, 20.9 and is therefore used in a vacuum. In the long-wave limit of this region, roughly 150–200 nm, the principal absorber is the oxygen Oxygen (pronounced /ˈɒksɨdʒɨn/, OK-si-jin, from the Greek roots ὀξύς (acid, literally "sharp", from the taste of acids) and -γενής (-genēs) (producer, literally begetter), is the element with atomic number 8 and represented by the symbol O. It is a member of the chalcogen group on the periodic table, and is a highly in air. Work in this region can be performed in an oxygen free atmosphere, pure nitrogen being commonly used, which avoids the need for a vacuum chamber.
See 1 E-7 m To help compare different orders of magnitude, this page lists lengths starting at 107 metres for a list of objects of comparable sizes.
Sources of UV
Natural sources of UV
The sun The Sun is the star at the center of the Solar System. It has a diameter of about 1,392,000 kilometers , about 109 times that of Earth, and its mass (about 2 × 1030 kilograms, 330,000 times that of Earth) accounts for about 99.86% of the total mass of the Solar System. About three quarters of the Sun's mass consists of hydrogen, while the rest is emits ultraviolet radiation in the UVA, UVB, and UVC bands. The Earth's ozone layer The ozone layer is a layer in Earth's atmosphere which contains relatively high concentrations of ozone . This layer absorbs 97–99% of the sun's high frequency ultraviolet light, which is potentially damaging to life on earth. Over 90% of the ozone in Earth's atmosphere is present here. It is mainly located in the lower portion of the blocks 97-99% of this UV radiation from penetrating through the atmosphere.[4] 98.7% of the ultraviolet radiation that reaches the Earth's surface is UVA.[citation needed] (Some of the UVB and UVC radiation is responsible for the generation of the ozone layer.) Extremely hot stars emit proportionally more UV radiation than the sun; the star R136a1 R136a1 is a blue hypergiant star, currently on record as the most massive star known, at an estimated 265 solar masses. The star also holds the record for the most luminous at 8,700,000 times the luminosity of the Sun. It is a member of R136, a super star cluster near the center of the 30 Doradus complex , in the Large Magellanic Cloud. The mass has a thermal energy of 4.57 eV, which falls in the near-UV range.
Ordinary glass is partially transparent In the field of optics, transparency is the physical property of allowing light to pass through a material; translucency (also called translucence or translucidity) only allows light to pass through diffusely. The opposite property is opacity. Transparent materials are clear, while translucent ones cannot be seen through clearly to UVA but is opaque Opacity is the measure of impenetrability to electromagnetic or other kinds of radiation, especially visible light. In radiative transfer, it describes the absorption and scattering of radiation in a medium, such as a plasma, dielectric, shielding material, glass, etc. An opaque object is neither transparent nor translucent (allowing some light to to shorter wavelengths while Silica or quartz glass Fused quartz and fused silica are types of glass containing primarily silica in amorphous form. They are manufactured using several different processes. Note that glasses formed by the traditional 'melt-quench' methods (heating the material to melting temperatures, then rapidly cooling to the solid glass phase), are often referred to as 'vitreous',, depending on quality, can be transparent even to vacuum UV wavelengths. Ordinary window glass passes about 90% of the light above 350 nm, but blocks over 90% of the light below 300 nm.[5][6][7]
The onset of vacuum UV, 200 nm, is defined by the fact that ordinary air is opaque at shorter wavelengths. This opacity is due to the strong absorption of light of these wavelengths by oxygen in the air. Pure nitrogen (less than about 10 ppm oxygen) is transparent to wavelengths in the range of about 150–200 nm. This has wide practical significance now that semiconductor manufacturing processes are using wavelengths shorter than 200 nm. By working in oxygen-free gas, the equipment does not have to be built to withstand the pressure differences required to work in a vacuum. Some other scientific instruments, such as circular dichroism First pioneered by Jean-Baptiste Biot, Augustin Fresnel, and Aimé Cotton , circular dichroism refers to the differential absorption of left and right circularly polarized light.. This phenomenon is exhibited in the absorption bands of optically active chiral molecules. CD spectroscopy has a wide range of applications in many different fields spectrometers, are also commonly nitrogen purged and operate in this spectral region.
Extreme UV is characterized by a transition in the physics of interaction with matter: wavelengths longer than about 30 nm interact mainly with the chemical valence electrons In chemistry, valence electrons are the outermost electrons of an atom, which are important in determining how the atom reacts chemically with other atoms. Atoms with a complete shell of valence electrons tend to be chemically inert. Atoms with one or two valence electrons more than a closed shell are highly reactive because the extra electrons of matter, while wavelengths shorter than that interact mainly with inner shell electrons and nuclei. The long end of the EUV/XUV spectrum is set by a prominent He+ Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert monatomic gas that heads the noble gas group in the periodic table. Its boiling and melting points are the lowest among the elements and it exists only as a gas except spectral line A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range, compared with the nearby frequencies at 30.4 nm. XUV is strongly absorbed by most known materials, but it is possible to synthesize multilayer optics that reflect up to about 50% of XUV radiation at normal incidence In geometric optics, the angle of incidence is the angle between a ray incident on a surface and the line perpendicular to the surface at the point of incidence, called the normal. The ray can be formed by any wave: optical, acoustic, microwave, X-ray and so on. In the figure above, the red line representing a ray makes an angle θ with the normal. This technology has been used to make telescopes for solar imaging The Sun is the star at the center of the Solar System. It has a diameter of about 1,392,000 kilometers , about 109 times that of Earth, and its mass (about 2 × 1030 kilograms, 330,000 times that of Earth) accounts for about 99.86% of the total mass of the Solar System. About three quarters of the Sun's mass consists of hydrogen, while the rest is; it was pioneered by the NIXT and MSSTA sounding rockets in the 1990s; (current examples are SOHO The Solar and Heliospheric Observatory is a spacecraft that was launched on a Lockheed Martin Atlas IIAS launch vehicle on December 2, 1995 to study the Sun, which has also discovered a huge number of comets. It began normal operations in May 1996. It is a joint project of international cooperation between the European Space Agency (ESA) and NASA/EIT and TRACE) and for nanolithography Nanolithography refers to the fabrication of nanometer-scale structures, meaning patterns with at least one lateral dimension between the size of an individual atom and approximately 100 nm. Nanolithography is used during the fabrication of leading-edge semiconductor integrated circuits or nanoelectromechanical systems (NEMS) (printing of traces and devices on microchips In electronics, an integrated circuit is a miniaturized electronic circuit (consisting mainly of semiconductor devices, as well as passive components) that has been manufactured in the surface of a thin substrate of semiconductor material. Integrated circuits are used in almost all electronic equipment in use today and have revolutionized the).
Wed, 23 Jun 2010 09:06:24 GMT+00:00
MarketWatch (press release) The Company manufactures the viratech uv-400, which utilizes high-intensity germicidal ultraviolet radiation (UV-C) inside a killing chamber that goes ...
Mike Ginn
ue, 20 Jul 2010 18:26:00 GM
PC World The Digital Entertainment Content Ecosystem (DECE), a group of 58 Hollywood studios and technology companies, is pinning its hopes for the future of entertainment on . UltraViolet. , an online digital locker that would allow you ...
Q. I want to take pictures in ultraviolet. What are my options? I'd prefer a point and shoot digital camera, but I think I'm out of luck. I'd really like a camera that records a couple different wavelenghs of ultraviolet light as separate primary colors. Is there such a thing? Are there any camcorders that do this? How good is their picture quality for still images?
Asked by water_skipper - Mon May 28 20:04:40 2007 - - 1 Answers - 0 Comments
A. Almost all p&s have enough uv sensitivity to take an image in bright sunlight. What you need is a uv transmission filter that totally blocks the visible and ir. They are expensive but the larger photo houses on the internet carry them. As for colors you will get blue since all the light ends up in the blue channel because of the bayer filter. Google uv photography--there are a number of websites with more info
Answered by scribble - Tue May 29 17:08:08 2007
