When a certain metallic surface is irradiated with monochromatic light wavelength `lambda`, the stopping potential for photoelectric current is `3 V_(0)`. When the same surface is irradiated with light of wavelength `2 lambda`, the stopping potential is `V_(0)` The threshold wavelength for the given surface is

Options

A. `4 lambda`
B. `6 lambda`
C. `8 lambda`
D. `4 lambda/3`

Answer

A

Explanation

`(hc)/(lambda)=phi+c.(3v_(0)) " " ` in case I
`(hc)/(2 lambda)=phi + c. v_(0) " " `in case II
where `(hc)/(lambda_(0))=phi " "` (`lambda_(0)-` threshold wavelength)