we have that
wavelength of H-alpha (hα) is -------------- > 656.3 nm
measured wavelenght ------------------------ > 682 nm
Let
V---------------------> radial velocity
C-------------------- > is the speed of light which is equal to 300,000km/sec.
Doppler formula:
[(measured wavelenght - wavelength of hα)/ wavelength of hα] = V/C
V=C*[(measured wavelenght - wavelength of hα)/ wavelength of hα]
V=300000*[(682 - 656.3)/ 656.3]=11747.67 km/sec
the answer is 11747.67 km/sec
