CBSE Class 12 Physics 2019 Outside Delhi Set 2 Paper

Question : 7

Total: 9

What is the reason to operate photodiodes in reverse bias?
A ‌‌‌p - n photodiode is fabricated from a semiconductor with a band gap of range of 2.5 to 2.8‌eV. Calculate the range of wavelengths of the radiation which can be detected by the photodiode.

Solution:

(a) Reason
(b) Formula
(c) Calculation of range of wave length.
Reason:
Under reverse bias change in current with the change in intensity of light is more significant.
Calculation:
‌λ=‌

‌λ1=‌

6.63×10−34×3×108

2.5×1.6×10−19

=497×10−9m
‌λ2=‌

6.63×10−34×3×108

2.5×1.6×10−19

=444×10−9m
Range is 444×10−9m to 497×10−9m

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