Q. The threshold wavelength for a metal having work function $W_{0}$ is $\lambda_{0}$. What is the threshold wavelength for a metal whose work function is $W_{0}/2$
A) $4\lambda_{0}$
B) $2\lambda_{0}$
C) $\lambda_{0}/2$
D) $\lambda_{0}/4$
Explanation
(b) Work function $W_{0} = \frac{hc}{\lambda_{0}}$
where $\lambda_{0}$ is the threshold wavelength or $W_{0} \propto \frac{1}{\lambda_{0}}$
$\therefore\frac{W_{0}}{W_{0}'} = \frac{\lambda_{0}^{\ \ '}}{\lambda_{0}}\ or\ \frac{W_{0}}{W_{0}/2} = \frac{\lambda_{0}^{\ \ '}}{\lambda_{0}}\ or\ \lambda_{\ \ 0}^{'} = 2\lambda_{0}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.