Question

Electromagnetic waves are also affected by the Doppler shift in exactly the same manner as sound waves, with their frequency and wavelength changing depending on the motion of the object emitting them. Imagine if a torch was mounted on a rocket moving rapidly away from you. By analogy to the way motion affects the frequency of sound waves, would you expect the light from the torch to appear the same colour, slightly redder or slightly bluer? Briefly explain your reasoning.

Answer 1

As rocket moves away, wavelength of light emitted by it gets stretched and frequency decreases since speed of light is constant. So light color changes due to shortening wavelength towards red colour this phenomenon called redshift in cosmology. And nature of light seems radio waves because of increase in wavelength.