Q. What should be the velocity of an electron so that its momentum becomes equal to that of a photon of wavelength 5200 $\mathring{\mathrm{A}}$?
A) $700\ ms^{- 1}$
B) $1000\ ms^{- 1}$
C) $1400\ ms^{- 1}$
D) $2800\ ms^{- 1}$
Explanation
(c) Momentum, $p = mv = h/\lambda$
or $v = \frac{h}{m\lambda} = \frac{6.62 \times 10^{- 34}}{9.1 \times 10^{- 31} \times 5.2 \times 10^{- 7}}$
$= 1.4 \times 10^{3}\ ms^{- 1} = 1400\ ms^{- 1}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.