It was similar to a fluorescent lamp without the fluorescent coating on the tube, and produced greenish light. One of the first mercury vapor lamps invented by Peter Cooper Hewitt, 1903. But the Crookes tube, as it came to be known, produced little light because the vacuum in it was too good and thus lacked the trace amounts of gas that are needed for electrically stimulated luminescence. Thomson and X-rays in 1895 by Wilhelm Roentgen. Research conducted by Crookes and others ultimately led to the discovery of the electron in 1897 by J. That tube was evacuated by the highly effective mercury vacuum pump created by Hermann Sprengel. The most famous was the evacuated tube used for scientific research by William Crookes. Inquiries that began with the Geissler tube continued as even better vacuums were produced. Fluorescence occurred, but the tubes were very inefficient and had a short operating life. He went on to apply thin coatings of luminescent materials to the surfaces of these tubes. Alexandre Edmond Becquerel observed in 1859 that certain substances gave off light when they were placed in a Geissler tube. He also made the important observation that the glow in the tube shifted position when in proximity to an electromagnetic field. One of the first scientists to experiment with a Geissler tube was Julius Plücker who systematically described in 1858 the luminescent effects that occurred in a Geissler tube. More important, however, was its contribution to scientific research. 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. In comparison, the luminous efficacy of an incandescent bulb is only 16 lumens per watt.įluorescent lamp fixtures are more costly than incandescent lamps because they require a ballast to regulate the current through the lamp, but the lower energy cost typically offsets the higher initial 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 incandescent lamps. 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. Inside the lamp end of a preheat bi-pin lamp.
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