The threshold frequency for a photosensitive metal is 3.3 x 10¹⁴ Hz. If light of frequency 8.2 x 10¹⁴ Hz incident on this metal, the cut-off voltage for the photoelectric emission is nearly

Options

(a) 2 V
(b) 3 V
(c) 5 V
(d) 1 V

Correct Answer:

2 V

Explanation:

K.E = hv – hvₜₕ = eV₀ ( V₀ = cut off voltage)
V₀ = h/e (8.2 x 10¹⁴ – 3.3 x 10¹⁴)
= 6.6 x 10⁻³⁴ x 4.9 x 10¹⁴ / 1.6 x 10⁻¹⁹ = 2 V