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When a certain metallic surface is illuminated with monochromatic light of wavelength λ , the stopping potential for photoelectric current is 3 V 0 and when the same surface is illuminated with light of wavelength 2 λ , the stopping potential is V 0 . The threshold wavelength of this surface for photoelectric effect is

Options

  1. A6 λ
  2. B4 λ
  3. Cλ 4
  4. Dλ 6

Correct answer

B. 4 λ

Step-by-step solution

Using photoelectric equation, h f - h f 0 = 1 2 m v 2 = e V s Or h c λ - h c λ 0 = e V s For the first case, h c λ - h c λ 0 = e 3 V 0 ...(i) For the second case, h c 2 λ - h c λ 0 = e V 0 ...(ii) Solving λ 0 = 4 λ

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