LYCOS RETRIEVER 
Halogen
built 657 days ago
Halogen is a type of incandescent lamp. It has a tungsten filament just like a regular incandescent that you may use in your home... the bulb is filled with halogen gas. When an incandescent lamp (one which produces light by heating a tungsten filament) operates, tungsten from the filament is evaporated into the gas of the bulb and deposited on the glass wall. The bulb "burns out" when enough tungsten has evaporated from the filament so that electricity can no longer be conducted across it. The halogen gas in a halogen lamp carries the evaporated tungsten particles back to the filament and re-deposits them. This gives the lamp a longer life than regular A-line incandescent lamps and provides for a cleaner bulb wall for light to shine through.
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Halogen Lamps are ideal light sources for spectrophotometers as they provide broad band spectral radiation ranging from the ultraviolet, through the visible and into the infrared out to five microns. Some radiation output can be obtained at 320 and 340 nanometers.
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A Halogen incandescent lamp has a light spectrum as shown in the accompanying figure. The figure shows just the infrared end of the whole spectrum, which is limited by the resolution of the spectrum analyzer from 600nm to 1500nm, in the optical window, typical to fiber optic communication systems.
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Halogen light bulbs have a special gas inside their bulb containing halogens. The halogen gas facilitates the "halogen regenerative cycle" which means that the halogens carry the evaporated tungsten back to the filament instead of allowing it to deposit on the bulb wall. By placing the tungsten back on the filament instead of the wall, it delays the filament breaking due to lack of tungsten. Although the halogen cycle significantly increases the life of the light bulb, it cannot last forever because the halogen gasses cannot place the tungsten on a specific spot on the filament to avoid any place having too little tungsten and breaking.
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Halogen bulbs are ideal for most household lighting needs, either in fixtures or in lamps. At these discount prices, you'll be able to afford more of them, too. The blue-tinted light you'll get from halogen bulbs isn't quite as bright as that from xenon lamps, but then again xenon's a better fit for lab equipment and theater projectors - and halogen's plenty bright for most needs. Not only are they great in lamps, halogen bulbs are used in flashlights, motorcycle lights, and auto lights. You'll ... find quartz halogen bulbs in high-powered searchlights and other industrial-strength lighting.
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Halogen, being a highly reactive gas, reacts with the condensed particles, converting them into tungsten halide. Tungsten halide evaporates easily, and when particles reach the heated filament (due to running electricity) they break to release the halides, and the tungsten particles settle back on the filament. Due to this process, the evaporated particles of the filament are returned and the process of thinning of filament is slowed down. Thus the bulbs are long-lasting in comparison to incandescent lamps. Due to this halogen cycle, the inner surface of the bulb is always clean, leading to bright light even in aging halogen lamps.
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Halogen