![]() No more need for phosphors since such lamps emits directly in a spectral band between 350-375 nm.Įven simpler and without using a wood filter, it is possible to emit UV directly with LEDs. While current fluorescent tubes use three types of phosphors which, when excited by the spectral line at 254 nm, emit in red, green, and blue, black light fluorescent lamps only use a single phosphor emitting in the ‘UV-A, typically around 370 nm.Īn alternative is to use mercury lamps, but this time at high pressure. It is therefore necessary to transform the UV-C into UV-A by fluorescence. Slightly less effective but much easier to use than Wood’s glass, the envelopes of blacklight lamps currently on the market consist of a coating deposited on ordinary glass.īut to be considered a black light, the lamp must emit less energetic UV, called UV-A from 315 to 400 nm. In particular, the 405 nm spectral line of mercury gives light violet color. Only the ends of the visible are transmitted when the lamp is on. ![]() It is logically practically black in appearance. In practice, Wood’s glass contains a lot of nickel oxide. Used on lamps during the First World War, this invention made it possible to communicate at night with the invisible ultraviolet signal. The American physicist Robert Williams Wood invented at the beginning of the 20th-century glass with these properties. To create a black light, you have to filter the light by letting the UV pass and eliminating the visible, which is the complete opposite of ordinary glass. For more than 80 years, this is indeed the best technique used in fluorescent tubes. The best-controlled way to produce ultraviolet black light is to electrically discharge mercury vapors. It took several decades to understand that ultraviolet (visible), and thermal (infrared or invisible) rays formed a continuum constituting the spectrum of optical radiation. He realized that beyond violet, ultraviolet rays were able to oxidize silver chloride. In a more prosaic way, we are talking about invisible light here, for example, in nightclubs to illuminate any light clothing with ultraviolet.Ī black-light emits ultraviolet, this radiation highlighted in 1802 by the German physicist Johann Wilhelm Ritter. ![]() Blacklight is invisible ultraviolet light that allows fluorescent objects to radiate. In this illustrative guide, I am going to tell you all about black light photography. ![]()
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