Answer:
3.149×10^7 m/s
Explanation:
the frequency is shifted to lower value hence the star is receding the Earth.
[tex]f=f_0\sqrt{\frac{1-\beta}{1+\beta} }[/tex]................1
f= 0.9 f_0
putting the value in 1 we get
[tex]0.9f_0=f_0\sqrt{\frac{1-\beta}{1+\beta} }[/tex].
[tex]0.9=\sqrt{\frac{1-\beta}{1+\beta} }[/tex].
on solving we get
β= 0.1049
now
[tex]\frac{v}{c} = \beta[/tex]
v= 0.1049×3×10^8= 3.149×10^7 m/s
