The Doppler effect is applicable for

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 ............

It is believed that the universe is expanding and hence the distant stars are receding from us. Light from such a star will show:

In the hydrogen spectrum,the wavelength of the ${H_\alpha}$ line is $656 \ nm$,whereas in the spectrum of a distant galaxy,the ${H_\alpha}$ line wavelength is $706 \ nm$. The estimated speed of the galaxy with respect to the Earth is:

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......$\mathring{A}$

If a source of light is moving away from a stationary observer,then the frequency of light wave appears to change because of