I do not understand how the wavelength of sound changes depending on the distance between the moving source and the observer. Its as if the sound waves have foresight as to how far the objects is and adjust wavelength. Please explain.

This should answer your question...

 

http://www.scienceforums.net/forums/showthread.php?t=7069&highlight=doppler+effect+sound

This should answer your question...

 

http://www.scienceforums.net/forums/showthread.php?t=7069&highlight=doppler+effect+sound

 

That's really not a thread about the Doppler effect.

 

Sound is a physical disturbance of molecules. But the measurement of the length and frequency of the wave depends on the speed of motion between source and observer. It is not a dependence on distance.

I got it clarified through a friend. The wavelength is the distance between two crests or troughs and when the source is moving towards the observer, the distance between subsequent crests is shortenend and hence the reduced wavelength. The frequency however is the same. Only the apparent frequency changes. Do you not agree?

No. Because the wavelength has changed the frequency must also change.

 

One formula to show this would be:

[math]f \lambda = v[/math]

Where:

f = frequency

[math]\lambda[/math] = wavelength

v = velocity of the wave

 

So when the wavelength decreases the frequency must increase so that the wave continues to move at a constant velocity.

 

When two bodies are moving relative to each other it is the frequency change which makes you hear a sound at a different frequency to the source sound.