Ultrasound is used during a scan to monitor the movement of a tissue boundary in the heart of a foetus.
A transducer sends short ultrasound pulses into the body and detects echoes from the same boundary. The speed of ultrasound in the tissue is 1540 m/s.
The table shows the echo time at different times during one movement of the boundary.
| Time in ms\text{ms}ms | Echo time in μs\mu\text{s}μs |
|---|---|
| 0 | 72 |
| 100 | 68 |
| 200 | 64 |
| 300 | 68 |
| 400 | 72 |
Calculate the distance moved by the tissue boundary between 0 ms and 200 ms.
Describe the movement of the tissue boundary during the 400 ms shown in the table.
At the first scanner setting, a wave train containing 20 complete wavelengths is 15.4 mm long in the tissue.
Calculate the frequency of the ultrasound.
A second scanner setting produces ultrasound with a frequency of 5.0 MHz.
Explain which setting should be used to show smaller details of the tissue boundary.
112 exam-style questions on Edexcel GCSE Physics 4.3 Sound, ultrasound and infrasound, covering 4.3.1 Sound waves, vibrations and the human ear, 4.3.2 Ultrasound and infrasound, 4.3.3 Uses of ultrasound and infrasound, and 4.3.4 Sound waves passing between media. Each one has a worked solution and a mark scheme showing where the marks go.