..... Click the link for more information. between visible violet light and X rays; it ranges in wavelength from about 400 to 4 nanometers and in frequency from about 1015 to 1017 hertz. It is a component (less than 5%) of the sun's radiation and is also produced artificially in arc lamps, e.g., in the mercury arc lamp.
The ultraviolet radiation in sunlight is divided into three bands: UVA (320–400 nanometers), which can cause skin damage and may cause melanomatous skin cancer skin cancer, malignant tumor of the skin . The most common types of skin cancer are basal cell carcinoma, squamous cell carcinoma, and melanoma. Rarer forms include mycosis fungoides (a type of lymphoma) and Kaposi's sarcoma .
..... Click the link for more information. ; UVB (280–320 nanometers), stronger radiation that increases in the summer and is a common cause of sunburn suntan results from this attempt by the skin to protect itself. Light-skinned persons and infants are especially susceptible to ultraviolet rays because they lack sufficient protective skin pigment. Certain diseases and drugs may also increase photosensitivity.
..... Click the link for more information. and most common skin cancer; and UVC (below 280 nanometers), the strongest and potentially most harmful form. Much UVB and most UVC radiation is absorbed by the ozone layer ozone layer or ozonosphere, region of the stratosphere containing relatively high concentrations of ozone , located at altitudes of 12–30 mi (19–48 km) above the earth's surface.
..... Click the link for more information. of the atmosphere before it can reach the earth's surface; the depletion of this layer is increasing the amount of ultraviolet radiation that can pass through it. The radiation that does pass through is largely absorbed by ordinary window glass or impurities in the air (e.g., water, dust, and smoke) or is screened by clothing.
The National Weather Service's daily
UV index predicts how long it would take a light-skinned American to get a sunburn if exposed, unprotected, to the noonday sun, given the geographical location and the local weather. It ranges from 1 (about 60 minutes before the skin will burn) to a high of 10 (about 10 minutes before the skin will burn).
A small amount of sunlight is necessary for good health. Vitamin D is produced by the action of ultraviolet radiation on ergosterol, a substance present in the human skin and in some lower organisms (e.g., yeast), and treatment or prevention of rickets rickets or rachitis (rəkī`tĭs), bone disease caused by a deficiency of vitamin D or calcium.
..... Click the link for more information. often includes exposure of the body to natural or artificial ultraviolet light. The radiation also kills germs; it is widely used to sterilize rooms, exposed body tissues, blood plasma, and vaccines.
Ultraviolet radiation can be detected by the fluorescence fluorescence (fl
..... Click the link for more information. it induces in certain substances. It may also be detected by its photographic and ionizing effects. The long-wavelength, "soft" ultraviolet radiation, lying just outside the visible spectrum, is often referred to as black light; low intensity sources of this radiation are often used in mineral prospecting and in conjunction with bright-colored fluorescent pigments to produce unusual lighting effects.
Bibliography
See L. R. Koller, Ultraviolet Radiation (2d ed. 1965).
ultraviolet radiation
Portion of the electromagnetic spectrum extending from the violet end of visible light to the X-ray region. Ultraviolet (UV) radiation lies between wavelengths of about 400 nanometres and 10 nanometres, corresponding to frequencies of 7.5 × 1014 Hz to 3 × 1016 Hz. Most UV rays from the Sun are absorbed by the Earth's ozone layer. UV has low penetrating power, so its effects on humans are limited to the skin. These effects include stimulation of production of vitamin D, sunburn, suntan, aging signs, and carcinogenic changes. UV radiation is also used to treat jaundice in newborns, to sterilize equipment, and to produce artificial light.
ultraviolet radiation [¦əl·trə′vī·lət ‚rād·ē′ā·shən]
Ultraviolet radiation
Electromagnetic radiation in the wavelength range 4–400 nanometers. The ultraviolet region begins at the short wavelength (violet) limit of visibility and extends to the wavelength of long x-rays. It is loosely divided into the near (400–300 nm), far (300–200 nm), and extreme (below 200 nm) ultraviolet regions (see illustration). In the extreme ultraviolet, strong absorption of the radiation by air requires the use of evacuated apparatus; hence this region is called the vacuum ultraviolet. Important phenomena associated with ultraviolet radiation include biological effects and applications, the generation of fluorescence, and chemical analysis through characteristic absorption or fluorescence.
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Sources of ultraviolet radiation include the Sun (although much solar ultraviolet radiation is absorbed in the atmosphere); arcs of elements such as carbon, hydrogen, and mercury; and incandescent bodies.
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