Doppler shifted frequency - ultrasound

In summary, the question is asking for the Doppler shifted frequency of the reflected wave that comes back to the source when an object is moving towards it at a certain speed and the source is emitting sound waves at a certain frequency. The formula for calculating the Doppler shifted frequency for an observer approaching a source is f+ = (1+vo/v) fo, where vo is the object's speed and v is the speed of sound. For the reflected wave, the roles of source and observer are swapped, so the reflected frequency would be f- = (1-v/vo) fo. The moving object compresses the wave, increasing its frequency. This can be expressed mathematically using the Doppler formula.
  • #1
bcjochim07
374
0

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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  • #2
any help would be greatly appreciated
 
  • #3
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.
 
  • #4
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?
 

FAQ: Doppler shifted frequency - ultrasound

What is Doppler shifted frequency in ultrasound?

Doppler shifted frequency in ultrasound refers to the change in frequency of sound waves that occurs when they bounce off a moving object. This effect is used in ultrasound imaging to measure the speed and direction of blood flow in the body.

How does Doppler shifted frequency work in ultrasound?

In ultrasound, a transducer emits high frequency sound waves into the body. When these sound waves encounter a moving object, such as blood cells, they bounce off at a different frequency. This change in frequency is known as the Doppler shift and can be detected by the transducer to create an image of blood flow.

What factors can affect Doppler shifted frequency in ultrasound?

The speed and direction of the moving object, the angle of the sound waves, and the frequency of the sound waves can all affect the Doppler shift in ultrasound. Additionally, the density and composition of the tissue or fluid the sound waves are passing through can also impact the Doppler shift.

What are the uses of Doppler shifted frequency in ultrasound?

Doppler shifted frequency in ultrasound is primarily used in medical imaging to assess blood flow in the body. It is commonly used in obstetrics to monitor fetal heart rate and in cardiology to diagnose heart conditions. It can also be used to detect blood clots, tumors, and other abnormalities in the body.

What are the benefits and limitations of using Doppler shifted frequency in ultrasound?

The benefits of using Doppler shifted frequency in ultrasound include its non-invasive nature, real-time imaging capabilities, and ability to detect and diagnose various medical conditions. However, it also has limitations, such as difficulty in obtaining clear images in obese patients or in areas with a lot of gas or air, and the potential for inaccurate measurements if there is a high degree of turbulence in the blood flow.

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