# A doctor explains to a patient that an ultrasound scan will be used to check for a suspected abnormality in their liver. Explain how ultrasound waves are used to produce an image of the liver and detect any abnormality within it.

> OCR A-Level Physics A (H556) — 5.3 Astrophysics and cosmology · Explain · 5 marks

> Ultrasound waves have a frequency higher than 20 kHz, above the upper limit of human hearing. When used in medical imaging, a probe placed against the skin both emits ultrasound waves into the body and detects any waves that return.

## Mark scheme (5 marks)

1. Ultrasound waves are partially reflected at the boundary between two different media / tissues / organs
2. The remainder of the waves continue to pass through (are transmitted) into the next medium
3. The reflected waves are detected by the probe / receiver next to the emitter
4. The time between emission and detection of reflected waves is used to determine the depth / distance of each boundary
5. An abnormality causes a reflection at an unexpected depth / position, producing a different pattern of reflected waves compared to healthy tissue, allowing it to be detected

## Key terms

- [ultrasound waves](https://www.gradenine.co.uk/glossary/ultrasound-waves)

## Related

- [Revision notes for OCR A-Level Physics A (H556)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-doctor-explains-to-a-patient-dbcc9b72) · Published by Druglandscape Ltd.