Physics - Wave Optics Question with Solution | TestHub

Astronomers have observed that light coming from far away stars do not show the same spectrum as observed on Earth. Each wavelength is shifted slightly towards the red end of the spectrum. It is observed that the$1^{st}$line of Lyman series shows$121 \mathrm{nm}$on Earth, but from the star it shows$122 \mathrm{nm}$. The speed of the star with respect to Earth is close to