A photon of energy `4 eV` is incident on a metal surface whose work function is `2 eV`. The minimum reverse potential to be applied for stopping the emission of electrons is

Options

A. 2V
B. 4V
C. 6V
D. 8V

Answer

A

Explanation

When stopping potential is applied no electron will reach the cathode and the current will becomes zero
`therefore eV_(0)=(1)/(2)mv_max^(2)`
Also,`(1)/(2)mv_(max)^(2)`=hv-work fuction,
4 eV-2eV=2eV
`implieseV_(0)=2 eVimplies` stopping potential=2 V.