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Franck TOUBOUL 390180199 Project no. 42 פרנק טובול Thanks to the LED, the famous museum "The Louvre" expects to reduce its energy consumption by 73%. A light-emitting diode (LED) is a semiconductor light source. The LED consists of a chip of semiconducting material doped with impurities to create a p-n junction. As in other diodes, current flows easily from the p-side, or anode, to the n-side, or cathode, but not in the reverse direction. The free electrons in the N-type material are repelled by the negative electrode and drawn to the positive electrode. The holes in the P-type material move the other way. When the voltage difference between the electrodes is high enough, the electrons in the depletion zone are boosted out of their holes and begin moving freely again. The depletion zone disappears, and charge moves across the diode. When current flows across a diode, negative electrons move on way and positive holes move the other way. The holes exist at a lower energy level than the free electrons, so when a free electron falls it loses energy. This energy is emitted in the form of a light photon. The size of the electron’s “fall” determines the energy level of the photon, which determines its color (the Bohr model, studied in class explains this). A bigger fall produces a photon with a higher energy level and therefor a higher light frequency. LED applications ( a few of them…. ): LEDs have several advantages over conventional incandescent lamps. For one thing, they don't have a filament that will burn out, so they last much longer. Additionally, their small plastic bulb makes them a lot more durable. They also fit more easily into modern electronic circuits. Among other things, they form numbers on digital clocks, transmit information from remote controls, light up watches and tell you when your appliances are turned on. Collected together, they can form images on a jumbo television screen or illuminate a traffic light. Links: http://www.20minutes.fr/article/838166/louvre-illumine-diodes-electroluminescentes http://www.tetes-chercheuses.fr/magazines/numero-2/dossier/des-materiaux-comme-dessculptures-moleculaires-215/ mms://Ntstream2.ddns.ehv.campus.philips.com/efi/86090/ Lumalive.wmv http://phycomp.technion.ac.il/~webteach/phys3/ph114053/adler/bohr.html http://fr.wikipedia.org/wiki/Mod%C3%A8le_de_Bohr http://www.led-fr.net/fonctionnement.htm http://en.wikipedia.org/wiki/Energy_level http://en.wikipedia.org/wiki/Light-emitting_diode > other applications http://www.techno-science.net/?onglet=news&news=3194