A black light, also referred to as a UV-A light, ultraviolet light, is a lamp that emits ultraviolet radiation (UV) in the long-wave (near ultraviolet, UVA) range. Unfiltered lamps appear white when turned off and are designated BL; filtered lamps use the same phosphors but use Wood's glass to filter out visible light, and appear black when turned off. .
Black light sources may be specially designed fluorescent lamps, mercury vapor lamps, light-emitting diodes, or incandescent lamps. A filter to block visible light may be part of the bulb, or built into the light fixture. In medicine, forensics, and some other scientific fields, such a light source is referred to as a Wood's lamp (named after Robert Williams Wood).
Filtered black lights are essential when UV-A light without visible light is needed, particularly in observing fluorescence, the colored glow that many substances emit when exposed to UV. Black lights are employed for decorative and artistic lighting effects, for diagnostic and therapeutic uses in medicine, for the detection of substances tagged with fluorescent dyes, rock-hunting, for the curing of plastic resins and for attracting insects. Strong sources of long-wave ultraviolet light are used in tanning beds. Black light lamps are also used for the detection of counterfeit money. Many artificial ultraviolet sources are low power. Powerful ultraviolet sources present a hazard to eyes and skin; maintenance or adjustment of apparatus using these sources requires personal protective equipment such as goggles and gloves.
Read more about Black Light: Clinical Use, Safety, Uses
Famous quotes containing the words black and/or light:
“Richard. Give me a calendar.
Who saw the sun today?
Ratcliffe. Not I, my lord.
Richard. Then he disdains to shine, for by the book
He should have braved the east an hour ago.
A black day will it be to somebody.”
—William Shakespeare (1564–1616)
“Men’s hearts are cold. They are indifferent. Not all the coal that is dug warms the world. It remains indifferent to the lives of those who risk their life and health down in the blackness of the earth; who crawl through dark, choking crevices with only a bit of lamp on their caps to light their silent way; whose backs are bent with toil, whose very bones ache, whose happiness is sleep, and whose peace is death.”
—Mother Jones (1830–1930)