Question

A semiconductor of energy band gap of 3eV is exposed to light. Calculate the wavelength of light emitted by it

Answer 1

Answer:

To raise an electron from valence to conduction band , the energy required is

equal to the band gap in eV which has a value 1.5 eV as given

If a photon of energy E is absorbed by an electron then for the transfer

E = 1.5 eV = hv where h is plank's constant and

ν is the frequency.

as frequency ν=c, therefore

λ

h. c = 1.5 eV or

λ

λ=h. c

1.5eV

substituting the values of h and c and eV in Joules we get

λ =(6.62.10-³⁴) J - s. (3.10⁸m/s)

(1.5).1.60.10‐¹⁹J

λ=827.5nm