# An engineer uses ultrasound to check a metal pipeline for internal cracks without cutting it open. Explain how ultrasound waves can be used to detect a crack inside the pipeline and how the position of the crack can be determined.

> OCR A-Level Physics A (H556) — 5.2 Circular motion and gravitational fields · Explain · 5 marks

> Ultrasound pulses are sent into the metal pipeline from one end. A receiver placed at the same end detects any reflected pulses. The speed of ultrasound through the metal is known.

## Mark scheme (5 marks)

1. Ultrasound waves travel through the metal pipeline until they reach a boundary
2. At the boundary between the metal and the crack (or air gap), the ultrasound waves are partially reflected back
3. The reflected waves are detected by the receiver / detector
4. A crack causes reflections to return earlier / after a shorter time than reflections from the far end of the pipeline
5. The distance to the crack can be found because the speed of ultrasound is constant and the time between emission and detection of the reflected pulse is measured (distance = speed × half the time)

## 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/an-engineer-uses-ultrasound-to-check-4f8bf2b9) · Published by Druglandscape Ltd.