Answer: The correct answer is "monitor blood flow".
Step-by-step explanation:
Doppler effect is the phenomenon in which there is apparent change in the frequency ( increase or decrease) when there is a relative motion between the observer and source.
The wavelength of the wave is inversely proportional to the frequency.
Doppler effect is used in hospitals to monitor blood flow. It is used to measure the motion within the body.
Ultrasonic flow meter is a medical device which measures the velocity of blood flows in arteries and veins.
Transducer of ultrasonic flow meter consists of receiver and transmitter. It sets the frequency of the ultrasonic waves and then it is transmitted by the transmitter. Then, it will reflect back from the blood cells.
The blood cells are in motion so the wavelength of the reflected wave will get shortened.
Doppler effect is an effective tool in diagnosis of vascular problem.