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Fluorescent lighting (fluorescent tubes and lamps)
Inside a fluorescent tube, two luminescence phenomena come into play : fluorescence and electroluminescence. Under the action of an electric field, electrons collide with the mercury vapour atoms that fill the tube. These atoms are thus brought to an excited state and return to their original state by emitting an ultraviolet radiation. This radiation excites luminophors that form a layer covering the inside of the tube, and which emit fluorescence in the blue, red and green. The superposition of these three lights in the retina gives the impression of white light.
Fluorescent lamps, so-called fluocompact lamps, operate on a similar principle. The tube has a smaller diameter and is wound on itself. Fluorescent lighting is much more economical than incandescent lighting because the emission of incandescent lamps is mainly located in the infrared, hence the significant heat generated. In addition, fluorescent tubes and lamps have a much longer service life (several thousand hours). That is why the good old light bulbs will have virtually disappeared from the market by 2016, according to a European Union directive.
Laboratoire de photophysique et photochimie supramoléculaires et macromoléculaires, CNRS-ENS Cachan
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