# Explain why ultrasound can be used to distinguish between two different soft tissues that are next to each other inside the body.

> AQA A-Level Physics (7408) — 3.10.4 Non-ionising Imaging · Explain · 5 marks

> Ultrasound is used in medical imaging to produce pictures of internal structures without exposing patients to ionising radiation.

## Mark scheme (5 marks)

1. Ultrasound is partially reflected at a boundary between two different tissues
2. Reflection occurs because the two tissues have different densities / acoustic properties
3. The reflected pulse travels back to the detector / transducer
4. The time taken for the pulse to return is used to calculate the depth / position of the boundary
5. Different boundaries produce separate echoes / signals, allowing the two tissues to be distinguished / an image to be built up

## Key terms

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

## Related

- [Revision notes for AQA A-Level Physics (7408)](https://www.gradenine.co.uk/learn)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-ultrasound-can-be-used-03726318) · Published by Druglandscape Ltd.