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

Options

(a) 4000 nm
(b) 6000 nm
(c) 4000Å
(d) 6000Å

Correct Answer:

4000Å

Explanation:

λₘₐₓ = hc / E
= 6.6 x 10⁻³⁴ x 3 x 10⁸ / 2.5 x 1.6 x 10⁻¹⁹ = 5000Å
The wavelength detected by photodiode should be less than λₘₐₓ. Hence it can detect a signal of wavelength 4000Å.