Astronomers can tell whether a light source approaches or recedes from Earth by
A)its temperature.
B)its change in temperature.
C)its absorption spectra.
D)the Doppler effect.
E)all of the above

Question

Quizplus · Accepted Answer

The correct choice is the Doppler effect. This is because the Doppler effect is the shift in the observed frequency of a wave when the source or observer is moving towards or away from the other. This can be used to determine whether a light source is approaching or receding from Earth. The other choices (temperature, change in temperature, and absorption spectra) may provide valuable information about the light source, but they do not specifically indicate whether it is moving towards or away from Earth.

Astronomers Can Tell Whether a Light Source Approaches or Recedes