CBSE Class 10 Answered

A light emitting diode is simply a forward biased p-n junction, which emits light when energised.

 

In a forward biased p -n junction, the electrons of the n- region and holes of p -region are pushed towards the junction where electron hole recombination taken place. As the electrons are in higher conduction band on n-side and holes are in lower valence band on p -side, the energy difference appears in the form of heat or light radiation during the process of recombination.

The semiconductor used in LED is chosen according to the wavelength of the emitted light.

Advantages of LED over conventional incandescent lamps are as follows:

(i) Low operational voltage and less power consumption

(ii) Fast action and no warm up time required.