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) $10^{3}ms^{- 1}$
B) $1.2 \times 10^{3}ms^{- 1}$
C) $1.4 \times 10^{3}ms^{- 1}$
D) $2.8 \times 10^{3}ms^{- 1}$
Explanation
(c) $mv = \frac{h}{\lambda}$
or $v = \frac{h}{m\lambda} = \frac{6.6 \times 10^{- 34}}{9.1 \times 10^{- 31} \times 5200 \times 10^{- 10}}$
$= 1.4 \times 10^{3}\ ms^{- 1}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.