# Explain how the principle of superposition accounts for the formation of a standing wave when a transverse wave on a stretched string reflects from a fixed end.

> IB DP Physics Higher Level (2023 syllabus) — C.2 Wave model · Explain · 4 marks

> A transverse progressive wave travels along a stretched string and undergoes reflection at a fixed end, producing a standing wave pattern.

## Mark scheme (4 marks)

1. The incident wave and the reflected wave travel in opposite directions along the string with the same frequency (and speed/wavelength).
2. The principle of superposition states that the resultant displacement at any point is the vector sum (algebraic sum) of the displacements of the two waves at that point.
3. At certain points (nodes) the two waves are always in antiphase, so their displacements cancel at all times, giving zero resultant displacement.
4. At antinodes the waves are always in phase, so their displacements reinforce to give maximum amplitude, resulting in a pattern that does not travel along the string.

## Key terms

- [principle of superposition](https://www.gradenine.co.uk/glossary/principle-of-superposition)
- [standing wave](https://www.gradenine.co.uk/glossary/standing-wave)

## Related

- [Revision notes for IB DP Physics Higher Level (2023 syllabus)](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/explain-how-the-principle-of-superposition-66b1186e) · Published by Druglandscape Ltd.