Q. A star is moving away from the earth with a velocity of $100\ km/s$. If the velocity of light is $3 \times 10^{8}m/s$ then the shift of its spectral line of wavelength $5700\ \mathring{\mathrm{A}}$ due to Doppler’s effect will be
A) $0.63\mathring{\mathrm{A}}$
B) $1.90\mathring{\mathrm{A}}$
C) $3.80\mathring{\mathrm{A}}$
D) $5.70\mathring{\mathrm{A}}$
Explanation
(b) $\mathrm{\Delta}\lambda = \lambda\frac{v}{c} = 5700 \times \frac{100 \times 10^{3}}{3 \times 10^{8}} = 1.90\mathring{\mathrm{A}}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.