How the Doppler effect works

Imagine you are standing in the middle of a road and a car is coming towards you. The driver sounds the horn so that nothing unpleasant happens, and you hear the horn very loudly, at a high pitch, and step out of the way. However, as the car moves away from you, the sound of the horn seems to change even though the source itself does not. The reason behind this phenomenon can be explained with the Doppler effect. Before going into detailed questions such as “How does Doppler effect work” or “what is the Doppler shift”, let us start by answering the most basic question: “What is the Doppler effect?“ Sheldon, the genius from The Big Bang Theory, defines the Doppler effect as “It is the apparent change in the frequency of a wave caused by relative motion between the source of the wave and the observer.” The definition can be hard to grasp but to simplify it, think of something that is emitting waves whether a star emitting light or a police siren emitting sound. We see the Doppler effect happening with the