A certain echocardiogram uses ultrasounds with a frequency f = 6.1130 MHz. The speed of sound in blood is 1570 m/s. The patient is aligned so that blood is flowing through the heart directly towards the transducer (the transducer produces and detects the ultrasound waves).

Question

If blood flows through the artery being measured at a speed of 39.79 cm/s, what frequency signal would be detected by a red blood cell in the artery? Give your answer to four decimal places.

Answer 1

what frequency does the blood hear?
for observer toward source:
f' = f (v+Vobserver)/v
f' =6.113*10^6(1570+.3979)/1570
calculate f'

the blood particle serves as a transponder sending back a signal at that f'
now the source is moving toward the observer
f" = f' v/(v-vs)
f" = f' (1570)/(1570-.3979)
so we want f"