Doppler Effect

Doppler Effect

Introduction : In our day to day life we come across lots of phenomenon like a train approaching toward us or moving away from us. We have noticed that as the train approach towards us we are able to hear the sound of high pitch and as the train moves away we are able to notice that the pitch of sound goes on decreasing. This change in the pitch was first studied by Christian Doppler and this phenomenon is called as Doppler Effect. We are going to understand this topic in detail.

Listener as well as Source is stationary

Listener is stationary and Source is approaching toward listener

Doppler Effect can be studied in three different cases:

1) Source Moving and Listener Stationary

2) Source  Stationary and Listener Moving

3) Source Moving and Listener Moving

1) Source Moving and Listener Stationary :

a) Source is approaching towards listeners

Source is approaching towards Stationary listener

let us consider a source of sound moving towards an stationary listener with velocity V_s. The source is producing frequency of ղ and wavelength λ, the aparant frequency heard by listener is ղ_a as shown in fig 2. As the source moves towards listener the wavelength reduces and changes to λ1 and the velocity of sound is V.

Mathematically,

From Fig,

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b)  Source is moving away from listener

Source is moving away from Stationary listener

let us consider a source of sound moving away from a stationary listener with velocity V_s. The source is producing frequency of ղ and wavelength λ, the aparant frequency heard by listener is ղ_a as shown in fig 2. As the source moves away from listener the wavelength increases and changes to λ1 and the velocity of sound is V.

Mathematically,

From Fig,

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