It is extremely noticeable when police sirens or ambulance emergency vans rise in pitch as they approach us, and then eventually the pitch lowers down when they go off away from us into the distance. This is referred to as Doppler effect. More recently, the Doppler effect took centre-stage as investigators used it to trace the Malaysian aircraft Flight 370's disappearance.
The purpose of this post is to introduce in simple terms the concept of Doppler effect, what it is about and it's effect, and not to quantify intricate scientific formulations of frequency and the relationship of source and observer velocities.
