AIPMT | 2015Current Electricity and Electrical InstrumentHard
Question
A certain metallic surface is illuminated with monochromatic light of wavelength, λ. The stopping potential for photo-electric current for this light is 3V0. if the same surface is illuminated with light of wavelength 2λ, the stopping potential is V0. The threshold wavelength for this surface for photoelectric effect is :-
Options
A.4 λ
B.
C.
D.6 λ
Solution
Stopping potential = Incident energy - Emitted energy
Emitted energy is constant in both case hc/λ0 (λ0 = thresold wavelegth )
φ = hc/λ - hc/λ0
φ = hc/2λ - hc/λ0
λ0 = 4λ
Thus option A is correct
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