How is a standing wave produced on a stretched string?

A wave travelling along the string and the wave reflected back from the fixed end travel in opposite directions and superpose, giving a standing wave.

Explain why a standing wave transfers no energy along the string.

The two travelling waves carry equal energy in opposite directions, so there is no net transfer of energy along the string.

Describe how the displacement varies along one loop of a standing wave at the instant of maximum displacement.

It rises from zero at one node to a maximum at the antinode and falls back to zero at the next node, with every point of that loop on the same side of the axis.

OCR A-Level Physics B H557

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Waves and Quantum Behaviour

Standing waves on strings

3 things to know
Components 01, 02 and 03

Overview

Recall questions on how standing waves form on a string, nodes and antinodes and their spacing, why no energy is transferred, displacement and phase within and between loops, fundamental and harmonic wavelengths, calculating wave speed, counting nodes, the effect of tension, why only certain frequencies resonate, and driving a string with a vibration generator.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What is a node on a standing wave?

Key term

What is an antinode on a standing wave?

Evaluation

How far apart are adjacent nodes on a standing wave?

Questions from this subtopic

Each one with the model answer underneath.

1
How is a standing wave produced on a stretched string?
Model answer
A wave travelling along the string and the wave reflected back from the fixed end travel in opposite directions and superpose, giving a standing wave.
2
What is a node on a standing wave?
Model answer
A node is a point where the two travelling waves are always in antiphase, so the displacement there is zero at all times.
3
What is an antinode on a standing wave?
Model answer
An antinode is a point where the two travelling waves are always in phase, so the amplitude of oscillation there is a maximum.
4
How far apart are adjacent nodes on a standing wave?
Model answer
Adjacent nodes are half a wavelength apart.
5
Explain why a standing wave transfers no energy along the string.
Model answer
The two travelling waves carry equal energy in opposite directions, so there is no net transfer of energy along the string.
6
Describe how the displacement varies along one loop of a standing wave at the instant of maximum displacement.
Model answer
It rises from zero at one node to a maximum at the antinode and falls back to zero at the next node, with every point of that loop on the same side of the axis.

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