- u. A (UVA) u. radiation from 320 to 400 nm that causes skin tanning but is very weakly sunburn-producing and carcinogenic.
- u. B (UVB) u. radiation from 290 to 320 nm that most effectively causes sunburning and tanning; excessive UVB exposure is a cause of cancer of fair skin.
- u. C u. radiation from 200 to 290 nm; UVC in sunlight does not reach the surface of the earth; germicidal and mercury arc lamps may cause sunburn and photokeratitis.
- extravital u. having wavelengths of 2900 to 1850 Å.
- intravital u. having wavelengths of 3900 to 3200 Å.
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ul·tra·vi·o·let .əl-trə-'vī-(ə-)lət adj
1) situated beyond the visible spectrum at its violet end used of radiation having a wavelength shorter than wavelengths of visible light and longer than those of X-rays
2) relating to, producing, or employing ultraviolet radiation
ultraviolet n ultraviolet radiation
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ul·tra·vi·o·let (ul″trə-viґə-lət) beyond the violet end of the spectrum; said of electromagnetic rays or radiation between the violet rays and the x-rays, that is, with wavelengths between 200 and 400 nm. These rays have powerful actinic and chemical properties, inducing sunburn and tanning of the skin and producing ergocalciferol (vitamin D2) by their action on ergosterol in the skin.Medical dictionary. 2011.