Q. Assuming photoemission to take place, the factor by which the maximum velocity of the emitted photoelectrons changes when the wavelength of the incident radiation is increased four times, is
A) 4
B) 1/4
C) 2
D) 1/2
Explanation
(d) $\frac{hc}{\lambda} = W_{0} + \frac{1}{2}mv_{\max}^{2}$
Assuming $W_{0}$ to be negligible in comparison to $\frac{hc}{\lambda}$
$i.e.\ v_{\max}^{2} \propto \frac{1}{\lambda} \Rightarrow v_{\max} \propto \frac{1}{\sqrt{\lambda}}$
[On increasing wavelength $\lambda$ to $4\lambda,\ v_{\max}$ becomes half]
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.