Question

Light of wavelength 'λ' falls on a metal having work function \[\frac {hc}{λ_0}\]. Photoelectric effect will take place only if (λ₀ is the threshold wavelength) ______.

Options

• λ ≥ λ₀

• λ ≥ 2λ₀

• λ ≤ λ₀

• λ ≥ = 4 λ₀

Answer 1

Light of wavelength 'λ' falls on a metal having work function \[\frac {hc}{λ_0}\]. Photoelectric effect will take place only if (λ₀ is the threshold wavelength) λ ≤ λ₀.

Explanation:

Work function(𝜙) is the minimum energy required for emission of photoelectrons thus, for photoelectric emission;

⇒ hv = 𝜙 + K.E.

⇒ hv ≥ 𝜙 ⇒ hv ≥ hv₀

⇒ \[\frac {hc}{λ}\] ≥ \[\frac {hc}{λ_0}\] ⇒ λ₀ ≥ λ

⇒ λ ≤ λ₀.