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

To find the beat frequency between the emitted waves and the waves reflected from blood cells, we need to use the Doppler effect equation:

Î”f = (2 * v_r * f) / c

where:
Î”f 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:

Î”f = (2 * 0.15 * 5.0 * 10^6) / 1540

Now, let's calculate the beat frequency.