What is a LED used for?

Answer 1

LED's or `light emitting diodes' are solid state lights, meaning that they have no filament, which generate their light as power is applied to a junction which could be made up of many different materials such as gallium arsenide. Depending on the materials used, the light can be several different colors ranging from red to white and all colors between. Many times in the epoxy shell in which the electronic junction is encapsulated, they'll add an additional `doping' compound to assist in the light producing a different or enhanced color. For instance a white LED is usually a blue LED which is `doped' to produce a white light. Over a period of time, the white LED will start to get bluish as it ages and the doping `wears out'.