Q 12-10-098JEE MainJEE Main 2022 (26 Jun, Shift 2)Easy
For a specific wavelength $670\ \text{nm}$ of light coming from a galaxy moving with velocity $v$, the observed wavelength is $670.7\ \text{nm}$. The value of $v$ is
Answer: (B) $3.13\times10^5\ \text{m s}^{-1}$
For $v\ll c$, $\dfrac{\Delta\lambda}{\lambda} = \dfrac vc$:
$$v = 3\times10^8\times\frac{0.7}{670}\approx3.13\times10^5\ \text{m s}^{-1}$$
Solution by Sreeraj P, M.Sc Physics