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A certain metallic surface is illuminated with monochromatic light of wavelength λ . The stopping potential for photo-electric current for this light is 3 V 0 . If the same surface is illuminated with light of wavelength 2 λ , the stopping potential is V 0 . The threshold wavelength for this surface for the 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 Einstein's photoelectric equation e V s = E - ϕ V s = h c λ e - h c λ 0 e 3 V 0 = h c λ e - h c λ 0 e ...(i) V 0 = h c 2 λ e - h c λ 0 e ...(ii) by solving (i) and (ii) 0 = - h c 2 λ e + 2 hc λ 0 e λ 0 = 4 λ

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