Q. Light of frequency v falls on material of threshold frequency $v_{0}.$ Maximum kinetic energy of emitted electron is proportional to
A) $v - v_{0}$
B) $v$
C) $\sqrt{v - v_{0}}$
D) $v_{0}$
Explanation
(a) When light falls on a metallic surface, ejection of photoelectron results. In this process, conservation of energy holds.
Thus, from law of conservation of energy, the energy imparted by the photon
=maximum kinetic energy of the emitted electron +work function of the metal.
Or $\ \ \ hv =$(KE)$_{max}$ +$\phi$
but $\phi = {hv}_{0},\ v_{0}$ being threshold frequency.
$\therefore\ \ \ \ \ \ \ \ (KE)_{\max =}hv - hv_{0}\ \ \ \ \ \ \ \ \ $
$\ \ \ \ \ \ $or $\ (KE)\max\ \propto v - v_{0}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.