Doppler shifted frequency - ultrasound

AI Thread Summary
The discussion revolves around calculating the Doppler shifted frequency of a reflected wave from a moving object towards a stationary sound source. The initial formula used is for the frequency perceived by the moving object, which is f+ = (1 + vo/v) fo. The key point is that when the wave reflects back, the roles of the source and observer switch, requiring the application of the Doppler effect again. This results in a new frequency calculation for the reflected wave, taking into account the phase shift and the compression of the wave due to the object's motion. Understanding the interchange of roles is crucial for solving the problem accurately.
bcjochim07
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Homework Statement


An object is moving at speed vo toward a source at rest that is emitting sounds waves with frequency fo. What is the doppler shifted frequency of the reflected wave that comes back to the source?


Homework Equations





The Attempt at a Solution



If I use the doppler formula for an observer approaching a source : f+ = (1+vo/v) fo

This is the frequency seen by the moving object. But I'm not sure how to proceed. I think that the reflected wave would have a phase shift of pi, so does this question have something to with the superposition of the reflected waves and the waves coming from the source? I need a little nudge in the right direction.

Thanks
 
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any help would be greatly appreciated
 
I think that the the object moving at the wave compresses it, thus increasing frequency, but I'm not sure how to express this mathematically.
 
Hi bcjochim07,

You've already found the frequency received by the moving object. For the reflected wave, the roles of source and observer are swapped. Do you see what to do now?
 

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