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Question: A p – n photodiode is made of a material with band gap of 2 eV. The minimum frequency of the radiati...

A p – n photodiode is made of a material with band gap of 2 eV. The minimum frequency of the radiation that can be absorbed by the material is nearly

(Take hc = 1240 eV nm)

A

1×1014Hz1 \times 10^{14}Hz

B

20×1014Hz20 \times 10^{14}Hz

C

10×1014Hz10 \times 10^{14}Hz

D

5×1014Hz5 \times 10^{14}Hz

Answer

5×1014Hz5 \times 10^{14}Hz

Explanation

Solution

: Here, Eg=2eVE_{g} = 2eV

Wavelength of radiation corresponding to this energy is

λ=hcEg=1240eVnm2eV=620nm\lambda = \frac{hc}{E_{g}} = \frac{1240eVnm}{2eV} = 620nm

Frequencyυ=cλ=3×108ms1620×109m=5×1014Hz\upsilon = \frac{c}{\lambda} = \frac{3 \times 10^{8}ms^{- 1}}{620 \times 10^{- 9}m} = 5 \times 10^{14}Hz