Question

Due to Doppler’s effect the shift in wavelength observed is $0.1\mathring{A}$ for a star producing wavelength $6000\mathring{A}$. Velocity of recession of the star will be

• A. 5 km/s
• B. 25 km/s
• C. 20 km/s
• D. 10 km/s

Answer 1

Answer: (A)

The formula for Doppler shift $\frac{\Delta \lambda }{\lambda }=\frac{v}{c}$
$v=\frac{\Delta \lambda }{\lambda }.c=\frac{0.1}{6000}\times 3\times 10^8=0.5\times 10^4=5km{s}^{-1}$