Due to the Doppler effect,the shift in wavelength observed is $0.1\;\mathring{A}$,for a star producing a wavelength of $6000\;\mathring{A}$. The velocity of recession of the star will be ....... $km/s$.

$A$ rocket is moving away from the earth at a speed of $6 \times 10^7 \ m/s$. The rocket has blue light in it. What will be the wavelength of light recorded by an observer on the earth in $\mathring A$? (Wavelength of blue light $\lambda = 4600 \ \mathring A$)

$A$ star emitting light of wavelength $5896 \ \mathring{A}$ is moving away from the earth with a speed of $3600 \ km/s$. The wavelength of light observed on earth will be:
($c = 3 \times 10^8 \ m/s$ is the speed of light)

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 sound waves,the Doppler formula for frequency shift differs slightly between the two situations:
$(i)$ source at rest; observer moving,and
$(ii)$ source moving; observer at rest.
The exact Doppler formulas for the case of light waves in vacuum are,however,strictly identical for these situations. Explain why this should be so. Would you expect the formulas to be strictly identical for the two situations in case of light travelling in a medium?

What speed (in $km/s$) should a galaxy move with respect to us so that the sodium line at $589.0 \;nm$ is observed at $589.6 \;nm$?