$A$ light source approaches the observer with velocity $0.8 c$. The Doppler shift for the light of wavelength $5500 \ \mathring{A}$ is.....$\mathring{A}$.

$A$ rocket is moving towards the moon with a speed $v$. The astronaut in the rocket sends signals of frequency $f$ towards the moon and receives them back after reflection from the moon. What will be the frequency of the signal received by the astronaut? (Assume $v << c$)

The $6563\,\mathring{A}$ $H_{\alpha}$ line emitted by hydrogen in a star is found to be redshifted by $15\,\mathring{A}$. Estimate the speed with which the star is receding from the Earth.

If a star emitting light of wavelength $5000\,\mathring{A}$ is moving towards Earth with a velocity of $1.5 \times 10^6\,\text{m/s}$,then the shift in the wavelength due to Doppler's effect will be......$\mathring{A}$

What is the Doppler effect for light? Derive the formula for the Doppler shift.

$A$ 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 $\lambda = 4600 \ \mathring A$)