The lowest frequency of light that will cause the emission of photoelectrons from the surface of a metal (for which work function is 1.65 eV) will be

Options

(a) 4×10¹⁰ Hz
(b) 4×10¹⁴ Hz
(c) 4×10¹¹ Hz
(d) 4×10¹⁵ Hz

Correct Answer:

4×10¹⁴ Hz

Explanation:

Maximum wavelength (in Å) = 12375 / ɸ (in eV)

⇒ λ₀ = 12375 / 1.65 = 7,500 Å = 7.5 × 10⁻⁷ m

Hence minimum frequency = ʋ₀ = c / λ₀

⇒ ʋ₀ = (3 × 10⁸) / (7.5 × 10⁻⁷) = 4 × 10¹⁴ Hz