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, who invented the original Wood's glass UV filters.Īlthough many other types of lamp emit ultraviolet light with visible light, 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. This stands for "blacklight".īlacklight sources may be specially designed fluorescent lamps, mercury-vapor lamps, light-emitting diodes (LEDs), lasers, or incandescent lamps. These tubes are made for use in " bug zapper" insect traps, and are identified by the industry designation "BL". A second type of lamp produces ultraviolet but does not have the filter material, so it produces more visible light and has a blue color when operating. Blacklight lamps which have this filter have a lighting industry designation that includes the letters "BLB". One type of lamp has a violet filter material, either on the bulb or in a separate glass filter in the lamp housing, which blocks most visible light and allows through UV, so the lamp has a dim violet glow when operating. The violet glow of a black light is not the UV light itself, but visible light that escapes being filtered out by the filter material in the glass envelope.Ī blacklight, also called a UV-A light, Wood's lamp, or ultraviolet light, is a lamp that emits long-wave ( UV-A) ultraviolet light and very little visible light. For other uses, see Black Light (disambiguation).
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