Question

A P-N photodiode is made of a material with a band gap of 2.0ev. The minimum frequency of the radiation that can be absorbed by the material is nearly (Take hc = 1240eVnm)

(A) 5 × 10¹⁴ Hz

(B) 20 × 10¹⁴ Hz

(C) 1 × 10¹⁴ Hz

(D) 10 × 10¹⁴ Hz

Answer 1

The correct option is (A) 5 × 10¹⁴ Hz.

Explanation:

 Band gap = 2eV

i.e. E_g = 2 eV = 2 × 1.6 × 10^–19 J

we know, E_g = hf hence f = (Eg / h)

∴ f = {(3.2 × 10^–19) / (6.62 × 10^–34)}

∴ f = 5 × 10¹⁴ Hz