Question

A light source of wavelenght ${}^{\prime }{\lambda }^{\prime }$ illuminates on a metal surface, a photoelectron of Kinetic energy $1eV$ is emitted. The another light source of wavelength $\frac{\lambda }{3}$ ejects photo electron from the same metal surface with Kinetic energy is $4eV$, the value of work function is

• A. 1 eV
• B. 2 eV
• C. 4 eV
• D. 0.5 eV

Answer 1

The correct option is D

0.5 eV

$\frac{hc}{\lambda }=w+1$

$3\frac{\lambda c}{\lambda }=w+4$

$3(w+1)=w+4$

$2w=1ev$

$w=0.5ev$