The full form of LED is:

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This question was previously asked in

RRB ALP Electronics Mechanic 23 Jan 2019 Official Paper (Shift 2)

Answer 1

Light Emitting Diode (LED)

F1 J.S 30.3.20 Pallavi D8

A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it.
When the diode is forward-biased, the minority electrons are sent from p → n while the minority holes are sent from n → p.
At the junction boundary, the concentration of minority carriers increases. The excess minority carriers at the junction recombine with the majority charges carriers.
The energy is released in the form of photons on recombination. In standard diodes, the energy is released in the form of heat. But in light-emitting diodes, the energy is released in the form of photons.
As the forward voltage increases, the intensity of the light increases and reaches a maximum.
The color of the light is determined by the energy required for electrons to cross the band gap of the semiconductor.