When a certain metallic surface is illuminated with monochromatic light of wavelength λ , the stopping…

When a certain metallic surface is illuminated with monochromatic light of wavelength λ, the stopping potential for photoelectric current is 3V0 and when the same surface is illuminated with light of wavelength 2λ, the stopping potential is V0. The threshold wavelength of this surface for photoelectric effect is
  1. 6λ
  2. 4λ
  3. λ4
  4. λ6

Solution

Using photoelectric equation, hf-hf0=12mv2=eVs
Or hcλ-hcλ0=eVs
For the first case, hcλ-hcλ0=e3V0   ...(i)
For the second case, hc2λ-hcλ0=eV0   ...(ii)
Solving λ0=4λ

Asked in: NEET 2015 (Phase 1)

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