# A hospital uses ultrasound waves to produce images of structures inside a patient's body. Explain how ultrasound waves are used to produce an image of an internal structure, and explain why ultrasound is preferred over X-rays for repeated or routine scanning of soft tissue.

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

> Ultrasound scanners emit high-frequency sound waves into the body. These waves travel through different tissues and organs before returning to the scanner's detector.

## Mark scheme (5 marks)

1. Ultrasound waves are partially reflected at the boundary between two different media (e.g. between different tissues or organs)
2. The remainder of the waves continue to travel through (are transmitted) and can reflect at further boundaries
3. The time between emitting the ultrasound and detecting the reflected waves is used to determine the distance to each boundary / build up an image
4. X-rays can cause cell damage or mutations (and potentially cancer), whereas ultrasound does not cause cell damage
5. Ultrasound is a non-invasive method that is safe for repeated scanning, making it preferable for routine or repeated examinations (e.g. foetal scanning)

## 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-hospital-uses-ultrasound-waves-to-0a378766) · Published by Druglandscape Ltd.