When a certain metallic surface is illuminated with monochromatic light of wavelength `lamda`, the stopping potential for photoelectric current is `3V_0` and when the same surface is illuminated with light of wavelength `2lamda`, the stopping potential is `V_0`. The threshold wavelength of this surface for photoelectrice effect is

Options

A. `4 lambda`
B. `(lambda)/4`
C. `(lambda)/6`
D. `6 lambda`

Answer

A

Explanation

`(hc)/(lambda)=(hc)/(lambda_(0))+e. 3V_(0).....(i)`
`(hc)/(2lambda)=(hc)/(lambda_(0))+e.V_(0)......(ii)xx3`
`(i)-3(ii)`
`(hc)/(lambda)-(3hc)/(2lambda)=(hc)/(lambda_(0))-(3hc)/(lambda_(0))`
`-1/(2lambda)=-2/(lambda_(0)) implies lambda_(0)=4lambda`