1.

A p-n photodiode is fabricated from a semiconductor with a band gap of 2.5 eV. It can detect a signal of wavelength

Answer»

6000 Å
6000 nm
4000 nm
4000 Å

Solution :WAVELENGTH of light MUST be less than `lambda_(0), ` where `(hc)/(e lambda_(0)) ge E_(g)`
`rArr "" lambda_(0) le (hc)/(e E_(g)) or lambda le(6.63 xx 10^(-34) xx (3 xx 10^(8)))/((1.6 xx 10^(-19)) xx 2.5) or lambda_(0) le 5 xx 10^(-7)` m
Thus , light of wavelength 4000 Å `(or 4 xx 10^(-7) m)` only can be detected by the photodiode.


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