Question

If you find that the hydrogen alpha line in a star’s spectrum occurs at a wavelength of 656.45 nm, what is the star’s approximate radial velocity? Note that the rest wavelength of this line is 656.30 nm.

Answer 1

Answer:

The answer to the question is

The star’s approximate radial velocity is 68.52 km/s

Explanation:

To solve the

The formula is

$\frac{\lambda-\lambda_{rw}}{\lambda_{rw}} = \frac{v_r}{c}$ where

$v_r$ = velocity of the star

λ = Star's spectrum wavelength = 656.45 nm

$\lambda_{rw}$ = Rest wavelength = 656.30 nm

c = Speed of light = 299 792 458 m / s

Therefore we have

$\frac{656.45-656.30}{656.30} =\frac{v_r}{299 792 458}$ or $v_r$ = 68518.7699 m/s or 68.52 km/s