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Light-emitting diode
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===Appearance=== * Color: LEDs can emit light of an intended color without using any color filters as traditional lighting methods need. This is more efficient and can lower initial costs. * Cool light: In contrast to most light sources, LEDs radiate very little heat in the form of IR that can cause damage to sensitive objects or fabrics. Wasted energy is dispersed as heat through the base of the LED. * Color rendition: Most cool-[[#Other white LEDs|white LEDs]] have spectra that differ significantly from a [[black body]] radiator like the sun or an incandescent light. The spike at 460 nm and dip at 500 nm can make the color of objects [[color vision|appear differently]] under cool-white LED illumination than sunlight or incandescent sources, due to [[metamerism (color)|metamerism]],<ref>{{cite web|url = http://www.jimworthey.com/jimtalk2006feb.html|title = How White Light Works|author = Worthey, James A. |website = LRO Lighting Research Symposium, Light and Color|access-date = October 6, 2007}}</ref> red surfaces being rendered particularly poorly by typical phosphor-based cool-white LEDs. The same is true with green surfaces. The quality of color rendition of an LED is measured by the [[Color rendering index|Color Rendering Index (CRI)]]. * Dimming: LEDs can be [[Dimmer|dimmed]] either by [[pulse-width modulation]] or lowering the forward current.<ref>{{Cite book |last1=Narra |first1=Prathyusha |last2=Zinger |first2=D.S. |title=Conference Record of the 2004 IEEE Industry Applications Conference, 2004. 39th IAS Annual Meeting |chapter=An effective LED dimming approach |year=2004|volume=3 |pages= 1671β1676 |doi=10.1109/IAS.2004.1348695 |isbn=978-0-7803-8486-6 |s2cid=16372401 }}</ref> This pulse-width modulation is why LED lights, particularly headlights on cars, when viewed on camera or by some people, seem to flash or flicker. This is a type of [[stroboscopic effect]].
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