$A$ star moves away from Earth at a speed of $0.8 c$ while emitting light of frequency $6 \times 10^{14} \text{ Hz}$. What frequency will be observed on the Earth (in units of $10^{14} \text{ Hz}$)? ($c$ is the speed of light)

The wavelength of light coming from a star is $3700 \, \mathring{A}$. If the observed wavelength from Earth is $3737 \, \mathring{A}$,what is the velocity of the star? [$c = 3 \times 10^8 \, m/s$]

The Doppler effect in sound,in addition to the relative velocity between the source and the observer,also depends on the individual motion of the source and the observer relative to the medium. However,the Doppler effect in light depends only on the relative velocity between the source and the observer. The reason for this is:

$A$ galaxy is moving away from the Earth such that a spectral line at $600 \ nm$ is observed at $601 \ nm$. Then,the speed of the galaxy with respect to the Earth is (in $km \ s^{-1}$)

The $6563 \ \mathring{A}$ line emitted by a hydrogen atom in a star is found to be red-shifted by $5 \ \mathring{A}$. The speed with which the star is receding from the Earth is:

$A$ star emits light of $5500 \ \mathring{A}$ wavelength. If it appears blue to an observer on the Earth,it means: