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Ultraviolet (UV) radiation is electromagnetic radiation of a wavelength shorter than that of visible light, but longer than that of soft X-rays. It can be subdivided into near UV (380-200 nm wavelength) and extreme or vacuum UV (200–10 nm). When considering the effects of UV radiation on human health and the environment, the range of UV wavelengths is often subdivided into UVA (380–315 nm), also called Long Wave or "blacklight"; UV-B (315-280 nm), also called Medium Wave; and UVC (280-10 nm), also called Short Wave or "germicidal". See 1 E-7 m for a list of objects of comparable sizes.
The name means "beyond violet" (from Latin ultra, "beyond"), violet being the color of the shortest wavelengths of visible light. Some of the UV wavelengths are colloquially called black light, as it is invisible to the human eye. Some animals, including birds, reptiles, and insects such as beeThis article is about the insect. For the character B, see B. Andrenidae Anthophoridae Apidae Colletidae Ctenoplectridae Halictidae Heterogynaidae Megachilidae Melittidae Oxaeidae Sphecidae Stenotritidae Bees Apoidea superfamily) are flying insects, closes, can see into the near ultraviolet. Many fruits, flowers, and seeds stand out more strongly from the background in ultraviolet wavelengths as compared to human color vision. Many birds have patterns in their plumage that are invisible at usual wavelengths but seen in ultraviolet, and the urine of some animals is much easier to spot with ultraviolet.
The solarThe Sun (also called Sol is the star in our solar system. Planet Earth orbits the Sun. Other bodies that orbit the Sun include other planets, asteroids, meteoroids, comets and dust. Not all objects passing through the solar system have been orbitally capt coronaFor other meanings, see corona (disambiguation The corona is the luminous " atmosphere" of the Sun extending millions of kilometres into space, most easily seen during a total solar eclipse, but also observable in a coronagraph. An interesting feature of as seen in "deep" ultraviolet light at 17.1 nm by the Extreme ultraviolet Imaging TelescopeBastille Day Flare at the 19. 5 nm wavelength, as recorded by the EIT instrument The Extreme ultraviolet Imaging Telescope EIT is an instrument on the SOHO spacecraft used to obtain high-resolution images of the solar corona in the ultraviolet range. instrument aboard the SOHOThe Solar and Heliospheric Observatory SOHO is a spacecraft launched in 1995 to study the sun. It is a joint project of the European Space Agency (ESA) and NASA. SOHO Observatory Organization ESA, NASA Wavelength regime optical through UV, also magnetic i spacecraft The sunThe Sun (also called Sol is the star in our solar system. Planet Earth orbits the Sun. Other bodies that orbit the Sun include other planets, asteroids, meteoroids, comets and dust. Not all objects passing through the solar system have been orbitally capt emits ultraviolet light in the UVA, UVB, and UVC bands, but because of absorption in the atmosphereEarth's atmosphere is the layer of gases surrounding the planet Earth and retained by the Earth's gravity. It consists of nitrogen (78. 1% by volume) and oxygen (20. 9%), with small amounts of argon (0. 9%), carbon dioxide (variable, but around 0. 035%),'s ozone layerThe ozone layer is that part of the Earth's stratosphere which contains ozone. The total quantity of ozone in the ozone layer is not very large; if just the ozone were compressed to the pressure of the air at sea level, it would be only a few millimeters, 99% of the ultraviolet light that reaches the Earth's surface is UVA. (Some of the UVC light is responsible for the generation of the ozone.)
Ordinary glass is transparent to UVA but is opaque to shorter wavelengths. Silica or quartz glass, depending on quality, can be transparent even to vacuum UV wavelengths.
The onset of vacuum UV, 200 nm, is defined by the fact that ordinary air is opaque below this wavelength. 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 spectrometers, are also commonly nitrogen purged and operate in this spectral region.