Question

the apparent change in the wavelengths of a moving energy source is called the spectrum the doppler effect cosmic background radiation the big bang

Explanation:

The Doppler Effect is the apparent change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source. In the context of a moving energy - source, the change in wavelengths is known as the Doppler Effect. The spectrum is a range of wavelengths or frequencies. Cosmic background radiation is a form of electromagnetic radiation filling all space. The Big Bang is the scientific theory about the origin of the universe.

Answer:

B. the Doppler Effect