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photocell |
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photocellDevice for measuring or detecting light or other electromagnetic radiation, since its electrical state is altered by the effect of light. In a photoemissive cell, the radiation causes electrons to be emitted and a current to flow (photoelectric effect); a photovoltaic cell causes an electromotive force to be generated in the presence of light across the boundary of two substances. A photoconductive cell, which contains a semiconductor, increases its conductivity when exposed to electromagnetic radiation. Photocells are used for photographers' exposure meters, burglar and fire alarms, automatic doors, and in solar energy arrays. How to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit webmaster's page for free fun content. |
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