![]() ![]() By putting different chemicals inside, the tubes could be made to produce a variety of colors, and elaborate Geissler tubes were sold for entertainment. When a high voltage was applied between the electrodes, the inside of the tube lit up with a glow discharge. Geissler invented the first gas-discharge lamp, the Geissler tube, consisting of a partially evacuated glass tube with a metal electrode at either end. Little more was done with this phenomenon until 1856 when German glassblower Heinrich Geissler created a mercury vacuum pump that evacuated a glass tube to an extent not previously possible. The explanation relied on the nature of electricity and light phenomena as developed by the British scientists Michael Faraday in the 1840s and James Clerk Maxwell in the 1860s. One of the first to explain it was the Irish scientist Sir George Stokes from the University of Cambridge in 1852, who named the phenomenon "fluorescence" after fluorite, a mineral many of whose samples glow strongly because of impurities. By the middle of the 19th century, experimenters had observed a radiant glow emanating from partially evacuated glass vessels through which an electric current passed. The fluorescence of certain rocks and other substances had been observed for hundreds of years before its nature was understood. The United States Environmental Protection Agency recommends that fluorescent lamps be segregated from general waste for recycling or safe disposal, and some jurisdictions require recycling of them. Compact fluorescent lamps are now available in the same popular sizes as incandescents and are used as an energy-saving alternative in homes.īecause they contain mercury, many fluorescent lamps are classified as hazardous waste. For comparison, the luminous efficacy of an incandescent bulb may only be 16 lumens per watt.įluorescent lamp fixtures are more costly than incandescent lamps because, among other things, they require a ballast to regulate current through the lamp, but the initial cost is offset by a much lower running cost. The typical luminous efficacy of fluorescent lighting systems is 50–100 lumens per watt, several times the efficacy of incandescent bulbs with comparable light output. ![]() A fluorescent lamp converts electrical energy into useful light much more efficiently than an incandescent lamp. An electric current in the gas excites mercury vapor, which produces short-wave ultraviolet light that then causes a phosphor coating on the inside of the lamp to glow. Ī fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. In this lamp, the filament is surrounded by an oblong metal cathode shield, which helps reduce lamp end darkening. A "tombstone" style lamp-holder for T12 and T8 G13 bi-pin fluorescent lamps Inside the lamp end of a preheat G13 lamp. In the US, this symbol is now required on all mercury-containing fluorescent lamps. The (Hg) symbol indicates that this lamp contains mercury. Typical F71T12 100 W G13 bi-pin lamp used in tanning beds. Integrated compact fluorescent lamps of different shapes with E27 socket and an electronic ballast in the base. ![]()
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