Suppose an object is at rest and that it is emitting radiation. An observer at rest with respect to the object observes the radiation to be blueshifted from its original frequency. This blueshift can be caused by
A) the Doppler shift only.
B) the gravitational wavelength shift only.
C) the cosmological wavelength shift only.
D) either the gravitational or the cosmological wavelength shift

Question

Quizplus · Accepted Answer

The blueshift observed while the object is at rest can be caused by a gravitational wavelength shift, where radiation moves from a lower gravitational potential to a higher one, increasing its frequency.

Suppose an Object Is at Rest and That It Is