Photoelectric EffectHard
Question
When a centimeter thick surface is illuminated with light of wavelength λ, the stopping potential is V. When the same surface is illuminated by light of wavelength 2λ, the stopping potential is V/3. The threshold wavelength for the surface is :
Options
A.4λ/3
B.4λ
C.6λ
D.8λ/3
Solution
= φ + eV ......(i)
= φ + 
......(ii)⇒
= 2φ ⇒ φ = 
∴ λth = 4λ
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