For photoelectric emission from certain metal the cut - off frequency is `v`. If radiation of frequency `2 v` incident on the metal plate , the maximum possible velocity of the emitted electron will be (`m` is the electron mass).

Options

A. `2sqrt(hv//m)`
B. `sqrt(hv//(2m))`
C. `sqrt(hv//m)`
D. `sqrt(2hv//m)`

Answer

D

Explanation

`K_("max") = hv-phi_0`
`implies 1/2 mv^2 =h(2v)-hv`
`implies v sqrt((2hv)/m)`