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## Homework Statement

A Doppler blood flow unit emits ultrasound at 5.0 MHz.

What is the frequency shift of the ultrasound reflected from blood moving in an artery at a speed of 0.20 m/s?

Express your answer using two significant figures.

## Homework Equations

f' = f0(v/v-Vs)

frequency shift = f' - f0

f0 = 5*10^6 Hz

v = 1500 m/s (assumed)

Vs = 0.20 m/s

## The Attempt at a Solution

Plugging in the numbers we get the following equation for frequency shift:

(5*10^6)*[1500/(1500-0.2)]-5*10^6

Which comes out to approx 666 Hz. or 6.7 *10^2 Hz using 2 significant figures. However, this problem comes from an online hw set and according to that 6.7 *10^2 is not the correct solution.

Does anyone have an idea of what I am doing wrong? Thanks in advance for any and all help!

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