A light-emitting diode (LED)
is a semiconductor
light source. LEDs are used as indicator lamps in many devices, and are
increasingly used for lighting.
When a light-emitting diode
is forward biased (switched on), electrons
are able to recombine
with holes
within the device, releasing energy in the form of photons.
Light-emitting diodes are used in applications as diverse as replacements for aviation lighting, automotive lighting as well as in traffic signals. The compact size, the possibility of narrow bandwidth, switching speed, and extreme reliability of LEDs has allowed new text and video displays and sensors to be developed, while their high switching rates are also useful in advanced communications technology.