Laboratory measurements show hydrogen produces a spectral line at a wavelength of 486.1 nanometers (nm).A particular star's spectrum shows the same hydrogen line at a wavelength of 486.0 nm.What can we conclude?
A)The star is moving away from us.
B)The star is getting hotter.
C)The star is moving toward us.
D)The star is getting colder.

Question

Quizplus · Accepted Answer

This is an example of the Doppler effect which shows that the apparent wavelength of light emitted by a source changes if the source is moving relative to the observer. In this case, the star's spectral line of hydrogen is shifted to a shorter wavelength, indicating that the star is moving towards us.

Laboratory Measurements Show Hydrogen Produces a Spectral Line at a Wavelength