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LED,"Light Emitting Diode", is a electronical circuit element which spreads light. It was invented by Nick Holonyak in the 1962.
LED is semi-conductor. It's adventiges are low energy consuming, it's long life, it's small size and it's high yield. It's main ingredient is silicon.

When a light-emitting diode is switched on, electrons are able to recombine with electron holes within the device, releasing energy in the form of photons. This effect is called electroluminescence and the color of the light (corresponding to the energy of the photon) is determined by the energy gap of the semiconductor.

LEDs are used as indicator lamps in many devices and are increasingly used for other ligthing. Infrared LEDs are also used in the remote control units of many commercial products including televisions, DVD players, and other domestic appliances.