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GIPHOTOSTOCK / SCIENCE PHOTO LIBRARY GIPHOTOSTOCK / SCIENCE PHOTO LIBRARY
Macro of a white LED used in a flashlight. Over recent several years, high-power white light emitting diodes (LEDs) reached consumer price levels and found their use in flashlights. Compared to conventional lightbulbs, LEDs are more efficient, have longer battery lifetime, and are more durable. White LEDs are typically based on blue LEDs (InGaN, indium gallium nitride) coated with doped YAG (yttrium aluminum garnet) crystals which act as a phosphor, down-converting part of the blue radiation to a broad spectrum centered in the yellow. The resulting spectral mix has the appearance of white light to the human eye. Shown here is a 1-Watt LED used in a flashlight sold in the US by Energizer. September 2007.
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