How is a light emitting diode fabricated? Briefly explain the basic processes involved in the emission of spontaneous radiation from it. Write two advantages of LED lamps over the incandescent low power lamps. 

 

 
 
 
 
 

Answers (1)
S safeer

\Rightarrow The light-emitting diode (LED) is a heavily doped p-n junction diode which under forward bias emits spontaneous radiation.

\Rightarrow The diode is encapsulated with a transparent cover so that emitted light can come out.

WORKING :

\Rightarrow When the diode is forward biased, electrons are sent from n region to p region and holes are sent from p region to n region.

\Rightarrow At junction boundary, excess minority carriers recombine with majority carriers near the junction.

\Rightarrow On recombination, energy is released in the form of photons.

\Rightarrow When forward current is small, the light intensity is small. When forward current increases light intensity increases and reach a maximum.

ADVANTAGES : 

\Rightarrow Low operational voltage and less power.

\Rightarrow Long life and ruggedness.

\Rightarrow Fast action and no warm-up time required.

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