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Question:

A photoelectric surface is illuminated successively by monochromatic light of wavelengths λ and λ2. If the maximum kinetic energy of the emitted photoelectrons in the second case is 3 times that in the first case, the work function of the surface is :

3hcλ

hcλ

hc2λ

hc3λ

Solution:

The correct option is A
hc2λ
K.Eλ=hcλ−Φ
K.Eλ/2=hcλ/2−Φ
K.Eλ/2=3(K.Eλ)→Φ=hc2λ