# A student measures the width of a human hair as 0.00008 m. Explain how the student could express this measurement using an appropriate SI prefix, and state why using SI prefixes is useful in scientific work.

> AQA A-Level Physics (7408) — 3.1.1 Use of SI Units and Their Prefixes · Explain · 5 marks

## Mark scheme (5 marks)

1. Converts 0.00008 m correctly to 80 µm (micrometres) OR 0.08 mm (millimetres)
2. Identifies the correct prefix symbol used (µ for micro OR m for milli) and its meaning
3. States that SI prefixes avoid writing large numbers of zeros / very small or very large numbers
4. States that SI prefixes make values easier to read, compare, or communicate
5. States that SI prefixes are part of a universal/standardised system used by scientists worldwide, allowing consistency

## Key terms

- [SI prefix](https://www.gradenine.co.uk/glossary/si-prefix)

## Related

- [Revision notes for AQA A-Level Physics (7408)](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-student-measures-the-width-of-1020c8ca) · Published by Druglandscape Ltd.