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Physics

Module 3: Waves and Thermodynamics

The Doppler Effect and Beats

What are beats and the Doppler Effect?

In this post, we analyse qualitatively and quantitatively the relationships of the wave nature of sound to explain beats and the Doppler Effect, as a part of the Prelim Physics course under the module Waves and Thermodynamics and sub-part Sound Waves. Beats are the periodic and repeating fluctuations heard in the intensity of a sound when two sound waves of very similar frequencies interfere with one another. The Doppler Effect is the change in frequency of a wave in relation to an observer who is moving relative to the wave source.

  • Beats f_{beat} = | f_{2} - f_{1} |
  • Doppler Effect f' = f \frac{v_{wave} + v_{observer}}{v_{wave} - v_{source}}

 

Beats

The following video covers the definition and equation of beat frequencies, and how they can be visualised graphically.

 

The Doppler Effect

The following video will introduce you to the Doppler Effect, and the propagation of sound of a moving object.