Question

Suppose that a star has a spectrum that includes red, blue, and violet lines spaced in the pattern of the lines from hydrogen but the violet lines are at 444nm and 420nm instead of the usual 434nm and 410nm. From this evidence, you can conclude that the star is:___________

Answer 1

Answer:

It can be concluded that the star is moving away from the observer.

Explanation:

Spectral lines will be shifted to the blue part of the spectrum if the source of the observed light is moving  toward the observer, or to the red part of the spectrum when is moving away from the observer (that is known as the Doppler effect).

The wavelength at rest for this case is 434 nm and 410 nm ($\lambda_{0} = 434nm$, $\lambda_{0} = 410nm$)

$Redshift: \lambda_{measured} > \lambda_{0}$

$Blueshift: \lambda_{measured} < \lambda_{0}$

Since, $\lambda_{measured}$ (444nm) is greater than $\lambda_{0}$ (434 nm) and $\lambda_{measured}$ (420nm) is greater than $\lambda_{0}$ (410 nm), it can be concluded that the star is moving away from the observer