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Question: When a certain photosensitive surface is illuminated with monochromatic light of wavelength λ, the s...

When a certain photosensitive surface is illuminated with monochromatic light of wavelength λ, the stopping potential is 2V0. When the same surface is illuminated with monochromatic light of wavelength 2λ, the stopping potential is V0/2. The threshold wavelength for photo electric emission is –

A

1.5 λ

B

2.0 λ

C

2.5 λ

D

3λ

Answer

3λ

Explanation

Solution

2eV0 = – φ

hc2λ\frac { \mathrm { hc } } { 2 \lambda } – φ

φ = hcλ0\frac { \mathrm { hc } } { \lambda _ { 0 } }