In a laboratory, the Balmer-beta spectral line of hydrogen has a wavelength of 486.1 nm. If the line appears in a star's spectrum at 485.5 nm, what is the star's radial velocity (in km/s)

Use Doppler's formula to find the radial velocity of star.

Here,

= Radial Velocity

c = Speed of light

= Shift in wavelength

= Laboratory wavelength of spectral line

Rearrange for ,

Find shift in wavelength,

Replacing our values we have then,

Therefore the radial velocity of star is m/s

In this case the symbol of implies that the star is receding the observer and the wavelength turns to red, then is red shifted.

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explanation: