Question

A $p-n$ photodiode is made of a material with a band gap of $2\, eV$. The minimum frequency of the radiation that can be absorbed by the material is nearly (he = 1240 eV nm)

• A. $1 \times 10^{14}\, Hz$
• B. $20 \times 10^{14}\, Hz$
• C. $10 \times 10^{14}\, Hz$
• D. $5 \times 10^{14}\, Hz$

Answer 1

The Correct Option is D

Here, $E_g = 2\,eV$
Wavelength of radiation corresponding to this energy is
$\lambda = \frac{hc}{E_{g}} $
$ = \frac{1240 \,eV \,nm}{2 eV} $
$= 620\, nm $
Frequency $\upsilon$ $= \frac{c}{\lambda}$
$ = \frac{3\times 10^{8} ms^{-1}}{620\times 10^{-19} } $
$= 5\times 10^{14}\,Hz$