Q. The maximum velocity of an electron emitted by light of wavelength $\lambda$ incident on the surface of a metal of work function $\phi,$ is Where $h =$ Planck’s constant, $m =$ mass of electron and $c =$ speed of light
A) $\left\lbrack \frac{2(hc + \lambda\phi)}{m\lambda} \right\rbrack^{1/2}$
B) $\frac{2(hc - \lambda\phi)}{m}$
C) $\left\lbrack \frac{2(hc - \lambda\phi)}{m\lambda} \right\rbrack^{1/2}$
D) $\left\lbrack \frac{2(h\lambda - \phi)}{m} \right\rbrack^{1/2}$
Explanation
(c) According to Einstein’s photoelectric equation
$\frac{hc}{\lambda} = \phi + \frac{1}{2}mv^{2} \Rightarrow v = \left\lbrack \frac{2(hc - \lambda\phi)}{m\lambda} \right\rbrack^{1/2}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.