What is the Doppler Effect and how does it work?

[TyroneBorr]

Can someone explain the Doppler Effect in simple terms? I'm especially curious how it relates to sound or light waves in everyday life.

 

[BarryRaymo]

The Doppler Effect is the apparent change in frequency or wavelength of a wave when the source or observer is moving. As the source approaches, waves are compressed, creating a higher frequency or pitch. When it moves away, waves are stretched, producing a lower frequency. It applies to sound, light, and electromagnetic waves.