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Q.

Which of the following exhibit electroluminescence?

 A.

Bipolar transistor

 B.

Optical fiber

 C.

Light-emitting diode

 D.

PIN diode

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Solution:
Option(C) is correct

A light-emitting diode (LED) is a two-lead semiconductor light source. It is a pn-junction diode, which emits light when activated.

When a suitable voltage is applied to the leads, electrons are able to recombine with electron holes within the device, releasing energy in the form of photons.

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


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