Q. A light source approaches the observer with velocity $0.8\ c$. The Doppler shift for the light of wavelength $5500\mathring{\mathrm{A}}$ is
A) $4400\ \mathring{\mathrm{A}}$
B) $1833\ \mathring{\mathrm{A}}$
C) $3167\ \mathring{\mathrm{A}}$
D) $7333\ \mathring{\mathrm{A}}$
Explanation
(c) According to Doppler’s principle $\lambda^{'} = \lambda\sqrt{\frac{1 - v/c}{1 + v/c}}$ for $v = c$
$\lambda^{'} = 5500\sqrt{\frac{(1 - 0.8)}{1 + 0.8}} = 1833.3$
$\therefore$ Shift $= 5500 - 1833.3 = - 3666.7$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.