Question

A light having wavelength 300 nm fall on a metal surface. The work function of metal is 2.54 e V, what is stopping potential ?

• A. 2.3 V
• B. 2.59 V
• C. 1.59 V
• D. 1.29 V

Answer 1

Answer: (C)

1.59 V

Energy of incident radiation is given by:

$E=\frac{hc}{\lambda }=\frac{6.64\ast {10}^{-34}\ast 3\ast {10}^8}{300\ast {10}^{-9}}=6.64\ast {10}^{-19}=4.05eV$

The work function of the metal is equal to $2.54eV$
Hence the maximum kinetic energy of an ejected photoelectron would be $1.59eV$
And the stopping potential needed to stop this would be $1.59V$.