How is the spectrum of a bright-line emission spectrum changed from a cloud of interstellar gas that is moving away as opposed to a stationary one relative to us?
A) The bright lines will be shifted toward the blue part of the spectrum.
B) The emission spectrum would be turned into an absorption spectrum.
C) The bright lines will be shifted toward the red part of the spectrum.
D) Some bright lines would shift toward the red part of the spectrum and some would shift toward the blue part of the spectrum.

Question

Quizplus · Accepted Answer

When a cloud of interstellar gas is moving away from us, the light emitted by the cloud will be redshifted due to the Doppler effect. This means that the wavelength of the light will be stretched, causing the bright lines to shift toward the red part of the spectrum. Therefore, the correct answer is C.

How Is the Spectrum of a Bright-Line Emission Spectrum Changed