# Standing waves

A fixed pattern of nodes and antinodes made by two waves moving in opposite directions. Only certain frequencies fit.

Physics (university) · Part 05: Oscillations and waves · Card 9 of 11 · Last updated 2026-10-19

## Analogy

A guitar string vibrating in one big loop.

## Example

**Guitar string**

f1 = v / (2L)
f1 = 260 / 1.3
f1 = 200 Hz
f2 = 400 Hz

## In practice

A 0.65 m string with wave speed 260 m/s has a lowest note of 200 Hz.

## Practice

### Flashcards

- **What is a node?** A point on a standing wave that never moves.

### Interview questions

**Explain how a standing wave forms on a guitar string and find the first three frequencies for a 0.65 m string with wave speed 260 m/s.**

- Two waves moving opposite ways superpose
- Ends are nodes
- f_n = n v / 2L gives 200, 400, 600 Hz

## Questions people ask

### What are nodes and antinodes?

Nodes are points on a standing wave that stay still, where the two waves always cancel. Antinodes are points halfway between nodes where the movement is largest. The distance between two neighbouring nodes is half a wavelength, which helps when measuring wavelength on a string.

### Why do different instruments sound different at the same note?

Each instrument produces the main frequency plus a particular mix of higher harmonics. The mix gives the sound its timbre. A violin and a flute may both play 440 Hz, but the strengths of their overtones differ, so you can tell them apart.

## Related concepts

- [Wave speed](https://studyvisually.com/learn/science/physics-university/physics-university-part-5/physics-university-part-5-concept-6)
- [Simple harmonic motion](https://studyvisually.com/learn/science/physics-university/physics-university-part-5/physics-university-part-5-concept-1)
- [Period and frequency](https://studyvisually.com/learn/science/physics-university/physics-university-part-5/physics-university-part-5-concept-2)
- [Mass on a spring](https://studyvisually.com/learn/science/physics-university/physics-university-part-5/physics-university-part-5-concept-3)

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