Ultraviolet A
One of the three types of invisible light rays (together with ultraviolet B and ultraviolet C) given off by the sun. Although ultraviolet C is the most dangerous type of ultraviolet light in terms of its potential to harm life on earth, it cannot penetrate earth's protective ozone layer. Therefore, it poses no threat to human, animal or plant life on earth. Ultraviolet A and ultraviolet B, on the other hand, do penetrate the ozone layer in attenuated form and reach the surface of the planet. Because ultraviolet A is weaker than ultraviolet B, scientists long blamed ultraviolet B as the sole culprit in causing skin cancer in persons with a history of sunburn and repeated overexposure to ultraviolet radiation. Recent research, however, has also implicated ultraviolet A as a possible cause of skin cancer. In addition to natural light from the sun, artificial light from tanning lamps contains ultraviolet A and ultraviolet B. Electric arc lamps can also generate ultraviolet light to heat furnaces for melting and to enable motion-picture projectors to show movies. Though ultraviolet light can damage health, it can also maintain or improve health. When ultraviolet light strikes human skin, it triggers the production of vitamin D, which promotes the growth of bones and teeth.

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ultraviolet A -'ā n UVA

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(UVA) ultraviolet radiation with wavelengths between 320 and 400 nm; this constitutes over 99 per cent of the ultraviolet radiation reaching the surface of the earth. UVA enhances the harmful effects of ultraviolet B radiation and is also responsible for some photosensitivity reactions; it is used therapeutically in the treatment of a variety of skin disorders (see PUVA therapy, under therapy).

Medical dictionary. 2011.

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  • ultraviolet-A — ultravioletinis A spektras statusas T sritis Standartizacija ir metrologija apibrėžtis Ultravioletinės spektro srities (artimasis ultravioletas) dalis, esanti nuo 315 nm iki 380 nm. atitikmenys: angl. ultraviolet spectrum A vok. Ultraviolett A, n …   Penkiakalbis aiškinamasis metrologijos terminų žodynas

  • ultraviolet-A — ultravioletinis A spektras statusas T sritis fizika atitikmenys: angl. ultraviolet spectrum A vok. Ultraviolett A, n rus. спектр А ультрафиолетового излучения, m pranc. ultraviolet A, m …   Fizikos terminų žodynas

  • ultraviolet A — /ʌltrəˌvaɪələt ˈeɪ/ (say ultruh.vuyuhluht ay) noun a form of ultraviolet light which is less intense but has greater penetration than ultraviolet B. Abbrev.: UVA Compare ultraviolet B …   Australian English dictionary

  • ultraviolet A — noun : uva herein …   Useful english dictionary

  • ultraviolet à vide — vakuumo ultravioletas statusas T sritis fizika atitikmenys: angl. vacuum ultraviolet vok. Vakuumultraviolett, n rus. вакуумный ультрафиолет, m pranc. ultraviolet à vide, m …   Fizikos terminų žodynas

  • psoralen and ultraviolet A therapy — PUVA therapy. A type of photodynamic therapy used to treat skin conditions such as psoriasis, vitiligo, and skin nodules of cutaneous T cell lymphoma. The patient receives psoralen (a drug that becomes active when it is exposed to light) by mouth …   English dictionary of cancer terms

  • ULTRAVIOLET — L’ultraviolet est le domaine des radiations électromagnétiques s’étendant depuis la limite violette du spectre visible (400 nm) jusqu’à la région des rayons X mous, qu’il recouvre partiellement (cf. figure). Cette délimitation repose… …   Encyclopédie Universelle

  • Ultraviolet (disambiguation) — Ultraviolet refers to electromagnetic radiation with a wavelength shorter than that of visible light, but longer than soft X rays.Ultraviolet may also refer to:In film and television* Ultraviolet (TV serial), a 1998 British television miniseries… …   Wikipedia

  • Ultraviolet-visible spectroscopy — or ultraviolet visible spectrophotometry (UV/ VIS) involves the spectroscopy of photons in the UV visible region. It uses light in the visible and adjacent near ultraviolet (UV) and near infrared (NIR) ranges. In this region of the… …   Wikipedia

  • ultraviolet — ULTRAVIOLÉT, Ă, ultravioleţi, te, adj. (Despre radiaţiile electromagnetice; şi substantivat, f. pl.) Care are lungimea de undă mai mică decât lungimea de undă minimă a radiaţiilor vizibile. [pr.: vi o ] – Din fr. ultraviolet. Trimis de ana… …   Dicționar Român

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