Answer: It is used to learn about the behavior of the universe.
It was used by Hubble to measure velocities of galaxies.
It indicates galaxy motion through light wavelengths.
Explanation:
Doppler effect for light is the apparent change in the frequency of light when there is relative motion between the source of the light and the observer.
Scientists measure Doppler shift to understand the behavior of the universe. If there is red shift in the light coming from all the galaxies, it would mean that the universe is expanding. The red shift indicates the that the galaxies are moving away from earth and blue shift indicates that the galaxies are moving towards the Earth. It can be used to measure the velocities of the galaxies which was done by Hubble.
Thus, the correct options are: It is used to learn about the behavior of the universe.
It was used by Hubble to measure velocities of galaxies.
It indicates galaxy motion through light wavelengths.
