The Doppler effect is applicable for

The wavelength of light from a star is $0.4\%$ more than the corresponding wavelength on the Earth. The velocity of the star with respect to the Earth is:

For a specific wavelength $670 \; nm$ of light coming from a galaxy moving with velocity $v$,the observed wavelength is $670.7 \; nm$. The value of $v$ is ............

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:

Light coming from a star is observed to have a wavelength of $3737 \ \mathring{A}$,while its real wavelength is $3700 \ \mathring{A}$. The speed of the star relative to the earth is (Speed of light $c = 3 \times 10^8 \ m/s$).

With what speed should a galaxy move outward with respect to Earth so that the sodium-$D$ line at wavelength $5890 \ \mathring{A}$ is observed at $5896 \ \mathring{A}$? (in $\text{km/s}$)