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Silver has a work function of 4 .7 eV . When ultraviolet light of wavelength 100 nm is incident on it a potential of 7 .7 V is required to stop the photoelectrons from reaching the collector plate. The potential required to stop the photoelectrons, when light of wavelength 200 nm is incident on it, is

Options

  1. A15.4 V
  2. B2.35 V
  3. C3.85 V
  4. D1.5 V

Correct answer

D. 1.5 V

Step-by-step solution

e v 0 +   ϕ = h c λ and e v 0 ′ +   ϕ = h c λ ′ e v 0 ′ + ϕ e v 0 + ϕ = λ λ ′ = 100 200 = 1 2 2 e v 0 ′ + 2 ϕ = e v 0 +   ϕ e v 0 ′ = e v 0 - ϕ 2 = 7.7 - 4.7 2 = 1.5 V

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