Doppler Effect

What is Doppler Effect?

It's the apparent change in the frequency of a wave caused by relative motion between the source and the observer

Doppler effect Cases:- (The general relationship of observed frequencies)

Here how to determine the signs of the above law

See This Video For more clarification:- How To Solve Doppler Effect Physics Problems - Basic Introduction

Doppler effect cases:- (In Detail)

Case 1:- the observer is moving/ the sound source is static (Source Speed = zero)

• If the observer moves toward the static sound source (Then the observed frequency is greater than the source frequency)

(In this case:- Let's say that the sound wave takes originally 3 seconds to travel from the source until it reaches the observer, if the observer moves toward the source, then the sound wave will actually take less than 3 seconds to reach the observer)

• If the observer is moving away from the static sound source (Then the observed frequency is less than the source frequency)

(In this case:- Let's say that the sound wave takes originally 3 seconds to travel from the source until it reaches the observer, if the observer moves away from the source, then the sound wave will actually take more than 3 seconds to reach the observer)

Case 2:- the observer is static/ the audio source is moving (Observer Speed = zero)

• If the sound source moves toward the static observer (Then the observed frequency is greater than the source frequency)

(In this case:- you will hear the sound waves closer than if the source is static because the wavelength measured by the observer will be shorter than the source wavelength)

• If the sound source moves away from the static observer (Then the observed frequency will be less than the source frequency)

(In this case:- you will hear the sound waves farther than if the source is static because the wavelength measured by the observer will be longer than the source wavelength)

The Doppler effect also occurs in electromagnetic waves:-

• Stars that move toward Earth tend to be blue
• Stars that move away from Earth tend to be red