The potential difference that must be applied to stop the fastest photoelectrons emitted by a nickel surface , having work function `5.01 eV` , when ultraviolet light of `200 nm` falls on it , must be

Options

A. 2.4 V
B. `-1.2V`
C. `-2.4V`
D. `1.2V`

Answer

B

Explanation

Here,
Incident wavelength, `lamda = 200 nm`
Work function `phi_0 = 5.01 eV`
According to Einstein.s photoelectric equation
`eV_s = hupsilon - phi_0`
`eV_s = (hc)/lamda - phi_0`
where `V_s` is the stopping potential
`eV_s=((1240 eV nm))/((200 nm)) -5.01 eV = 6.2 eV - 5.01 eV =1.2 eV`
Stopping potential , `V_s = 1.2 V`
The potential difference that must be applied to stop photoelectrons `=- V_s = - 1.2 V`