ultraviolet light


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Related to ultraviolet light: visible light, infrared light, Ultraviolet Rays

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.

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

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.

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.

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.

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
References in periodicals archive ?
The glass was then exposed to ultraviolet light in one of two wavelengths: 340 nanometers, the same wavelength as in sunlight, and 254 nanometers.
Ultraviolet light, to the kind that Genesis Air Photocatalysis uses to combat airborne contamination, has been employed for years in hospitals and critical situations to kill bacteria, viruses, and other contaminants.
"Hepatocyte growth factor encourages cells to survive by preventing programmed cell death induced by ultraviolet light," Tschachler says.
The study's conclusion was that BioAstin significantly increased the amount of ultraviolet light energy required to produce skin reddening following daily ingestion of BioAstin for two weeks.
Ultraviolet light is used to kill bacteria, viruses and parasites, without the use of chemicals.
A hat with a wide brim (approximately 2.5 to 3 inches) can reduce ultraviolet light to the head, neck, and eyes by up to 50 percent.
Because ultraviolet light waves are very short (only a few millionths of 1 millimeter), their maximum penetration into human skin is usually less than that of visible light.
Photocatalysts use light to facilitate the elimination of contaminants, and they usually require ultraviolet light to do so.
Now, using ultraviolet light, astronomers have combined the full range of colors available to Hubble, stretching all the way from ultraviolet to near-infrared light.
When viewed in extreme ultraviolet light, the field lines are revealed due to particles spinning along them.
Led by Duke adjunct physics professor Henry Everitt, the researchers found that adding sulfur to ultra-fine powders of commonplace zinc oxide at about 1,000 degrees centigrade allows the preparation to convert invisible ultraviolet light into a remarkably bright and natural form of white light.
Shestopalov and his colleagues at Stanford University showed that, once activated by ultraviolet light, a molecule called a photoeaged morpholino can dampen a specific gene.

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