UV-light

A Black light or UV Light is a lamp emitting electromagnetic radiation that is almost exclusively in the soft near ultraviolet range, and emits very little visible light. The black light was invented by William H. Byler, in 1935.Fact: date=October 2008

In medicine, forensics, and some other scientific fields, such a light source is referred to as a Wood's lamp.

Fluorescent

Black light fluorescent tubes are typically made in the same fashion as normal fluorescent lights except that only one phosphor is used and the normally clear glass envelope of the bulb may be replaced by a deep-bluish-purple glass called Wood's glass, a nickel-oxide–doped glass, which blocks almost all visible light above 400 nanometers. In practice, partly due to cost but mainly because Wood's glass does not make a satisfactory material for lamp manufacture, the lamp will be made from normal glass and a relatively thin coating of a UV filtering material is applied to the exterior. The color of such lamps is often referred to in the trade as "blacklight blue" or "BLB." This is to distinguish these lamps from "bug zapper" blacklight ("BL") lamps that don't have the filter material''

The phosphor typically used for a near 368 to 371 nanometer emission peak is either europium-doped strontium fluoroborate (SrB₄O₇F:Eu²⁺) or europium-doped strontium borate (SrB₄O₇:Eu²⁺) while the phosphor used to produce a peak around 350 to 353 nanometers is lead-doped barium silicate (BaSi₂O₅:Pb⁺). "Blacklight Blue" lamps peak at 365 nm.

Manufacturers use different numbering systems for Black Light, UV-A, UV-B and Actinic tubes. Philips uses one system which seems to be falling into obsolescence, while the (German) Osram system seems to be dominating throughout the world outside North America. This table gives the details:

Peak Position approximated to the nearest decade.

Width between 50% intensity points on shoulders of peak.

This table lists tubes generating blue, U.V.A and U.V.B, in order of decreasing wavelength of the most intense peak. Approximate phosphor compositions, major manufacturer's type numbers and some uses are given as an overview of types available.

Osram Wood's glass tubes seem to use a fairly narrow band emitting phosphor, Europium activated Strontium Pyroborate, with a peak at about 370 nm, whereas North American and Philips Wood's glass tubes seem to use the wider band emitting, Lead activated Calcium Metasilicate, with a shorter wavelength peak at about 350 nm. These two seem to be the most commonly used, and different manufacturers offer either one or the other and often both.