A Doppler blood flow meter emits ultrasound at a frequency of 5.0 MHz. What is the beat frequency between the emitted waves and the waves reflected from blood cells moving away from the emitter at 0.15m/s? Assume that v_sound=1540m/s in blood.
The Doppler shift, delta f, of the blood cells moving away is 2 V/v_sound * 5.0 *10^6 Hz.
V = 0.15 m/s = the blood cell speed and v_sound = 1540 m/s.
The factor of 2 is there because the frequency is shifted twice (when received and when sent back).
delta f = 2*5*10^6*0.15/1540 = 974 Hz
The beat frequency (of the transmitted beam combined with the reflected beam)equals delta f
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perfect answer...thank you so much
To find the beat frequency between the emitted waves and the waves reflected from blood cells, we need to use the Doppler effect equation:
Δf = (2 * v_r * f) / c
where:
Δf is the change in frequency (beat frequency)
v_r is the velocity of the blood cells moving away from the emitter
f is the frequency of the emitted ultrasound waves
c is the speed of sound in the medium (blood in this case)
Given:
f = 5.0 MHz = 5.0 * 10^6 Hz
v_r = 0.15 m/s
c = 1540 m/s
Substituting the given values into the equation, we have:
Δf = (2 * 0.15 * 5.0 * 10^6) / 1540
Now, let's calculate the beat frequency.