A Doppler flow meter sends ultrasonic waves into a blood vessel. Blood flowing towards the meter reflects waves of what frequency?
ALower than the sent one
BHigher than the sent one
CEqual to the sent one
DDouble the sent one
Answer & Solution
Correct answer: B. Higher than the sent one
1. The meter transmits ultrasonic waves that are reflected by the moving blood cells.
2. Reflection from a moving object shifts the frequency, exactly as the Doppler effect predicts.
3. Blood moving towards the meter shifts the reflected sound to a higher frequency.
4. Blood moving away shifts it to a lower frequency, which is how the direction of flow is read.
5. An unchanged frequency would mean the blood was not moving relative to the meter at all.
_Source: Siyavula Physical Sciences Grade 12 (Everything Science, CC BY 4.0), Chapter 6: Doppler effect_
Related questions
An ambulance siren emits sound of frequency 400 Hz and the ambulance drives at 20 m/s straLight from a distant galaxy arrives with its spectral lines shifted towards longer wavelenA siren stands still while a cyclist rides straight towards it. What frequency does the cyA car with its hooter sounding drives straight towards you. What happens to the sound waveWhat does the Doppler effect describe?