Light from some stars shows an apparent change in frequency because of:
A)interference
B)refraction by layers of air
C)diffraction
D)reflection
E)relative motion

Question

Quizplus · Accepted Answer

This is the Doppler effect, where the frequency of light appears to change due to the relative motion between the observer and the source. As the star moves towards or away from the observer, the frequency of light shifts towards the blue or red end of the spectrum, respectively.

Light from Some Stars Shows an Apparent Change in Frequency