# Explain why the amplitude of a transverse wave decreases as it travels through a medium, even when no energy is transferred to neighbouring media.

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

> A transverse mechanical wave travels along a long, uniform string. An observer notes that the amplitude of the wave decreases with distance from the source, despite the string being well insulated from any surrounding medium.

## Mark scheme (4 marks)

1. The wave transfers energy from the source outward / the energy of the wave is related to the square of its amplitude.
2. Energy is absorbed/dissipated by the medium itself through internal friction or damping forces between particles of the medium.
3. As energy is removed from the wave, the amplitude decreases because the oscillating particles have less energy and so reach a smaller maximum displacement.
4. This process is called absorption/attenuation and is distinct from reflection or transmission losses; it results from the conversion of wave (mechanical) energy into thermal (internal) energy of the medium.

## Key terms

- [transverse wave](https://www.gradenine.co.uk/glossary/transverse-wave)
- [amplitude](https://www.gradenine.co.uk/glossary/amplitude)

## Related

- [Revision notes for IB DP Physics Standard 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-why-the-amplitude-of-a-2cb2df22) · Published by Druglandscape Ltd.