Answer:
As an object moves away from us, the sound or light waves emitted by the object are stretched out, which makes them have a lower pitch and moves them towards the red end of the electromagnetic spectrum, where light has a longer wavelength.
Step-by-step explanation:
Doppler shift example: Sound waves from a police car siren. The car is driving forwards. The sound waves in front of the car get bunched up and the sound waves behind the car get stretched out.
In the case of light waves, this is called redshift