The Doppler effect suggests that sound waves are relative to the observer. You know if an object is coming or going from the sound it makes. Light waves follow the Doppler effect also. However, instead of sound changing, you know if an object is coming or going _____.
A similar principle is observed with light as it is with sound. If an
object is moving away from you the wavelengths gets longer, and towards
the red light spectrum of the visible light spectrum, whereas if an
object is moving towards you the wavelength will decrease towards the
blue end of the spectrum
