Q. A star emitting light of wavelength $5896\ \mathring{\mathrm{A}}$ is moving away from the earth with a speed of $3600\ km/s$. The wavelength of light observed on earth will ($c = 3 \times 10^{8}m/s$ is the speed of light)
A) Decrease by $5825.25\ \mathring{\mathrm{A}}$
B) Increase by $5966.75\ \mathring{\mathrm{A}}$
C) Decrease by $70.75\ \mathring{\mathrm{A}}$
D) Increase by $70.75\ \mathring{\mathrm{A}}$
Explanation
(d) $\Delta\lambda = \frac{v}{c}\lambda = \frac{3600 \times 10^{3}}{3 \times 10^{8}} \times 5896 = 70.75\mathring{\mathrm{A}}$
So the increased wavelength of light is observed
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.