Question: Q. 11. Give reason for the following :
(i) High reverse voltage does not appear across a LED.
(ii) Sunlight is not always required for the working of a solar cell.
(iii) The electric field, of the junction of a Zener diode, is very high even for a small reverse bias voltage of about $5 \mathrm{~V}$.
U] [Delhi Comptt. 2016]
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Solution:
Ans. (i) It is because reverse break down voltage of LED is very low i.e., nearly $5 \mathrm{~V}$.
(ii) Because solar cell can work with any light whose photon energy is more than the band gap energy.
(iii) The heavy doping of $p$ and $n$ sides of $p-n$ junction, makes the depletion region very thin, hence for a small reverse bias voltage, electric field is very high.
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