Question

A Doppler blood flowmeter 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 0.15 m/s?

Answer 1

Step-by-step explanation:

Given

Frequency of source
`f=5\ MHz`

velocity of blood cells moving away
`v_l=0.15\ m/s`

assuming velocity of sound in blood is
`v=1540\ m/s`

Considering Doppler effect to get the apparent frequency

Frequency shift of a moving object is given by

`\Delta f=\pm 2f_s\cdot (v_0)/(v)`

Where
`\Delta f=`shift in frequency

`f_s=`Frequency of source

`v_0=`velocity of observer

`v=`velocity of sound in given media

`\Delta f=\pm 2\cdot 5\cdot (0.15)/(1540)`

`\Delta f=974\ Hz`