Answer:
V = 31200000 m/s = 31200km/s
Explanation:
when star recedes away from earth its wavelength will appear to increae
[tex]\frac{\Delta \lambda}{\lambda_o} =\frac{v}{c}[/tex]
where c is speed of light
[tex]\Delta \lambda[/tex] is change in wavelength
[tex]\lambda_o[/tex] is wavelength of star = 625 nm
therefore we have
solving for v
[tex]v = \frac{\Delta \lambda}{c}{\lamda_0}[/tex]
[tex]v = \frac{(690-625)\times 10^{-9}\times 3\times 10^8}{625\times 10^{-9}}[/tex]
V = 31200000 m/s = 31200km/s
