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

Answer

C

Explanation

Cutoff frequency = v
Work function `=phi =hv`
Use, `E=K.E. +phi`
`2hv=(1)/(2)mv^(2)+hv`
`(1)/(2)mv^(2)=2hv-hv=hv`
`v=sqrt((2hv)/(m))`