ultraviolet light

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ultraviolet light

The segment of the electromagnetic spectrum between 200 and 400 nm, including photons emitted during electronic transition states. UV-C (200–290 nm) is damaging to DNA and amino acids, but is blocked in the stratospheric ozone layer; UV-B (290–320 nm) is partially blocked by the ozone layer; UV-A (320–400 nm) is the least dangerous, but may still be hazardous with photosensitising medications (e.g., tetracyclines, thiazides), and in patients with lupus erythematosus and light sensitivity disorders (e.g., porphyria). UV-A suppresses delayed cutaneous hypersensitivity, causes photoageing and reduces serum carotenoids; the accelerating depletion of the stratospheric ozone is implicated in the increased incidence of cataract, and melanomas.

UV light may also damage the less sensitive purines, causing spontaneous depurination, leaving a “naked” deoxyribose residue in the DNA (apurinic sites). Repair of UV-light-induced DNA damage is defective in chromosomal breakage syndromes (e.g., xeroderma pigmentosa and Bloom syndrome). The mutational effect of UV light is not due to direct DNA damage, but rather occurs during the error-prone process of DNA repair.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

ultraviolet light

Ultraviolet radiation Physics The part of the invisible electromagnetic spectrum below violet, including photons emitted during electronic transition states Wavelength 100-400 nm Public health The electromagnetic spectrum between 200 nm and 400 nm which is emitted by the sun. See SPF, Sunscreen.
UV light types
UV-A Long wave, 'near' UV, black light; short wave UV-A–320–340 nm; long wave UV-A–340–400 nm; no UV-A absorbed by ozone layer
UV-B Middle UV, sunburn radiation UV-B–290–320 nm; most UV-B is absorbed by ozone layer
UV-C Short wave, far UV, germicidal radiation, ≤ 290 nm; absorbed by ozone layer; has no role in photobiology of natural sunlight
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.

ultraviolet light

Electromagnetic radiation of shorter wavelengths than visible light but longer wavelength than X-rays. Ultraviolet light is divided into three zones—UVA with wavelengths from 380 to 320 nanometres (billionth of a metre), UVB from 320 nm down to 290 nm and UVC from 290 nm down to one tenth of a nanometre. UVC and most of UVB are absorbed by the ozone layer in the earth's stratosphere. Ultraviolet light causes sunburning and damages the skin's elastic protein, collagen. It is also a major factor in the development of the skin cancers rodent ulcer (BASAL CELL CARCINOMA), MALIGNANT MELANOMA and SQUAMOUS CELL CARCINOMA. It causes PINGUECULA and PTERYGIUM in the eyes.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005

ultraviolet light or ultraviolet radiation (UV)

a type of electromagnetic radiation beyond the wavelength of visible violet light, ranging from 18,000 to 33,000 nm (see ELECTROMAGNETIC SPECTRUM). UV light is not an ionizing radiation like X-RAYS and can only penetrate a few cells. However, it is used as a powerful MUTAGEN of microorganisms to cause the formation of thymine DIMERS in DNA, and can be harmful to the human RETINA. Some organisms can detect UV light (see ENTOMOPHILY). UV is a common cause of skin cancers; see MELANOMA.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005

Ultraviolet (UV) light

A portion of the light spectrum not visible to the eye. Two bands of the UV spectrum, UVA and UVB, are used to treat psoriasis and other skin diseases.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.

Patient discussion about ultraviolet light

Q. what does a sun block cream do? and what are a UV rays?

A. It blocks out harmful Ultra violet rays from the skin as the previous entries have related; however it can also block your ability to produce vitamin D. If you live in a northerly area or one that receives limited sunlight, its recommended to get at least 15 minutes of sun a day (this is probably best done with minimal sunblock) and according to personnal sun sensitivity. Another thing to keep in mind is that sunblock works best if applied 20 minutes before sun exposure.

More discussions about ultraviolet light
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References in periodicals archive ?
UL 1995 distinguishes between UV-C lamps located within the AHU and duct-mounted or non-integral field-installed systems, which are predominantly found in residential applications.
UV-C is a low-cost solution to disinfect cooling coils, drain pans and duct surfaces that have accumulated mold and bacteria growth.
"The effectiveness of a UV-C system to inactivate microorganisms in the air and/or on surfaces has been amply demonstrated; the best results were obtained for the long-term irradiation of downstream coil surfaces to avoid fungal amplification on wet surfaces," notes a 2015 ASHRAE Position Document on Filtration and Air Cleaning.
UV-C sources help restore an AHU to its original operating capacity.