A star is moving away from earth and shift in spectral line of wavelength 5700 Ao is 1.90Ao. Velocity of the star is
Answer & explanation
Correct answer: option 4
$\Delta \lambda = \frac{v}{c}\lambda $
$\Rightarrow v = \frac{\Delta \lambda}{\lambda}c = \frac{1.9}{5700} 3\times 10^8 = 10^5m/s = 100km/s$