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A photoelectric surface is illuminated successively by monochromatic light of wavelength λ and λ/2. 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 of the material is :
(h = Planck's constant, c = speed of light)
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hc λ -
2hc λ -
hc 3λ -
hc 2λ
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Correct Option: D
Photoelectric equations
| Ek1max = | - φ ....(i) | λ |
| and Ek2max = | - φ | λ/2 |
| Ek2max = | - φ ....(ii) | λ |
From question, Ek2max = 3Ek1max Multiplying equation (i) by 3
| 3Ek1max = |  | - φ |  | ....(iii) | λ |
From equation (ii) and (iii)
| - 3φ = | - φ | |||
| λ | λ |
| ∴ φ (work function) = | 2λ |
