Light Emitting Diode(LED)

   

What is L.E.D?

ANS.It is a two lead semiconductor light source.It is also P-N junction which emits light when activated.When a suitable voltage is applied to the leads,electrons are able to recombine with electrons holes within the device,releasing energy in the forms of photons.

This effect is called electroluminescence, and the colour of the light is determined by the energy band gap of the semiconductor.

WORKING:

The charge carriers recombine in a forward biased P-N junction as the electrons cross from the N-region and recombine with the holes existing in the P-region.Free electrons are in the 

the conduction band of energy levels,while holes are in the valence energy band.Thus the energy of holes will be lesser than the energy levels of the electron.some portion of energy must be dissipated in order to recombine the electrons and the holes.This energy is emitted in form of heat and light.