-
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 photo-electric effect is
-
- 4λ
-
λ 4 -
λ 6 - 6λ
Correct Option: A
As we know,
| eVs = | - ψ | λ |
| 3eV0 = | - ψ ....(i) | λ |
| eV0 = | - ψ ....(ii) | λ |
| 3eV0 = | - 3ψ ....(iii) | 2λ |
Multiplying eqn. (2) by (3) and subtracting it from eqn (1)
| ψ = | 4λ |
So,threshold wavelength,
| λth = | = | = 4λ | ||
| λ | hc/4λ |
