Assuming photoemission to take place , the factor by which the maximum velocity of the emitted photoelectrons changes when the wavelength of the incident radiation is increased four times , is

Options

A. `4`
B. `(1)/(4)`
C. `2`
D. `(1)/(2)`

Answer

D

Explanation

`(hc )/(lambda) = W_(0) + (1)/(2) mv_(max)^(2)`.
Assuming `W_(0)` to be negligible in comparison to `(hc )/(lambda)`
i.e., `v_(max)^(2) prop (1)/(lambda) rArr v_(max) prop (1)/(sqrt(lambda))`.
(On increasing wavelength `lambda to 4 lambda , v_(max)` becomes half).