lighting: The Fluorescent Lamp

The Fluorescent Lamp

The French physicist A. E. Becquerel constructed a fluorescent lamp and described (1867) the preparation of fluorescent tubes basically similar to those made today. Considerable progress in developing fluorescent lighting was made in several European countries, and during the 1920s high-voltage fluorescent tubes were used in advertising signs. In the United States the first practical hot-cathode, low-voltage fluorescent lamp was marketed in 1938. This is the form of lamp still commonly used. It consists of a long, sealed glass tube with an electrode at each end; a small amount of mercury is contained within the tube. The inside surface of the tube is coated with a mixture of fluorescent powders. When an electric current is maintained through the lamp, the mercury becomes vaporized and gives off invisible ultraviolet radiation that is absorbed by the fluorescent coating. The coating then emits visible light. The fluorescent lamp is often easily distinguished by its tubular design—straight, circular, or bent in a U or other shape. Compact fluorescent lamps, usually designed to screw into the socket originally made for an incandescent lamp, are now also shaped to resemble the less efficient incandescent lamps that they are intended to replace.

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