# A student sets up a ripple tank and generates water waves of a fixed frequency. The student observes that when the waves pass through a gap whose width is much larger than the wavelength, very little spreading of the waves occurs. The student then reduces the gap width until it is approximately equal to the wavelength. Describe what the student observes about the waves after they pass through the narrower gap, and explain why the amount of spreading changes when the gap width is reduced.

> Cambridge International IGCSE Physics (0625) — 3.1 General properties of waves · Describe and Explain · 4 marks

## Mark scheme (4 marks)

1. The waves spread out (diffract) significantly / noticeably after passing through the narrower gap
2. The waves spread out in a semicircular / curved pattern beyond the gap
3. Diffraction is greatest when the gap size is of the same order of magnitude as the wavelength
4. The frequency, wavelength, and speed of the waves are unchanged by diffraction

## Key terms

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

## Related

- [Revision notes for Cambridge International IGCSE Physics (0625)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and 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-sets-up-a-ripple-bc30205c) · Published by Druglandscape Ltd.