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 ....... $km/s$.

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

Light from the constellation Virgo is observed to increase in wavelength by $0.4\%$. With respect to Earth,the constellation 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:

$A$ 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 $v << c$)

For an observer on the earth, if a spectral line of wavelength $6600 \, \text{Å}$ emitted by a star is found to be red shifted by $22 \, \text{Å}$, then the star is