The spectra of most galaxies show redshifts.This means that their spectral lines
A)always are in the red part of the visible spectrum.
B)have wavelengths that are longer than normal.
C)have wavelengths that are shorter than normal.
D)have a higher intensity in the red part of the spectrum.
E)have normal wavelengths,but absorption of light makes them appear red.

Question

Quizplus · Accepted Answer

Redshift of spectral lines means that the wavelengths of the spectral lines have been stretched and shifted towards longer wavelengths, which corresponds to lower frequencies. This is caused by the Doppler Effect, and is commonly observed in galaxies moving away from Earth due to the expansion of the universe.

The Spectra of Most Galaxies Show Redshifts