black light


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ultraviolet radiation

ultraviolet radiation, invisible electromagnetic radiation 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; UVB (280–320 nanometers), stronger radiation that increases in the summer and is a common cause of sunburn 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 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 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 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).

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black light

[′blak ‚līt]
(optics)
Invisible light, such as ultraviolet rays which fall on fluorescent materials and cause them to emit visible light.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

black light

Invisible ultraviolet electromagnetic energy near the visible spectrum; useful for exciting fluorescent paints, dyes, etc., so that they become visible.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.
References in periodicals archive ?
Classics by legendary auteurs, avant-garde works by film artists, genres, and genre mixes of many types, they all can be found in Black Light, because there is no one conception of black cinema, or one conception of black people," he added.
"Black light theatre actually relies on one simple optical illusion called aACAyblack box trick', as the performers who are dressed in black cannot be seen against a black background," he added.
"Organising the Black Light Show as part of DSF activities constitutes the biggest event organised by them as yet.
If the black light test works, it represents a real advance in observing how shot moves though the air at normal game contact ranges.
Black light connotes a certain psychedelic or nightclub vibe.
Angela Davis and Huey Newton posters stand guard on the walls in an off-campus apartment dimmed by black light. Incense burn and the silky crooning of the Stylistics set the mood.
Except for traditional state-approved ballet and folk dance, as well as a stagnant form of the 1950s dance/puppetry craze known as Black Light Theatre, Czech arts took a severe battering under 50 years of Communist rule.
This means that when the wings absorb a special type of light, called ultraviolet light (or "black light"), they give off a bright blue-green glow.
Flowers such as four-o'clocks and portulacas invented the fluorescent look long before the psychedelic 1960s with its black light posters, new research shows.
Yes, it's a very familiar problem, but doing the asking this time is Huddersfield-based Black Light Productions, one of the UK's fastest growing youth theatre production companies.
"If you put that stuff under a black light it shows like it's radioactive.
The company has introduced black light curable doming compounds that are specifically designed to cure under black light to hard crystal clear polymers.