11 mark
The Doppler effect is used to measure the speed of blood flow in arteries.
Which medical diagnostic method uses this technique?
barium scan
CAT scan
PET scan
ultrasound scan
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6.13 Ultrasound
11 mark
The table shows some data on two tissues in a patient.
| Tissue | Density | Acoustic impedance |
| X | ρ | 1.5 Z |
| Y | 1.3 ρ | Z |
Ultrasound in tissue X is incident at the boundary between the tissues X and Y.
What is the percentage of the ultrasound intensity reflected at the boundary?
1.7 %
4.0 %
13 %
20 %
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21 mark
A beam of ultrasound is incident normally at a boundary between two tissues F and G.
The table below shows some data on the two tissues.
| Tissue F | Tissue G | |
| Density of tissue | ρ | 1.2ρ |
| Speed of ultrasound in tissue | c | 1.5c |
What percentage of the intensity of the ultrasound is reflected at the boundary?
0.83%
8.2%
9.1%
29%
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