Stationary Waves (Edexcel International A Level Physics)

Revision Note

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Lindsay Gilmour



Stationary Waves

  • Stationary waves, or standing waves, are produced by the superposition of two waves of the same frequency and amplitude travelling in opposite directions
  • This is usually achieved by a travelling wave and its reflection. The superposition produces a wave pattern where the peaks and troughs do not move


Stationary wave formation, downloadable AS & A Level Physics revision notes

Formation of a stationary wave on a stretched spring fixed at one end


  • In this section, we will look at a few experiments that demonstrate stationary waves in everyday life


Stretched Strings

  • Vibrations caused by stationary waves on a stretched string produce sound
    • This is how stringed instruments, such as guitars or violins, work

  • This can be demonstrated by an oscillator vibrating a length of string under tension fixed at one end:

Stationary wave string, downloadable AS & A Level Physics revision notes

Stationary wave on a stretched string


  • As the frequency of the oscillator changes, standing waves with different numbers of minima (nodes) and maxima (antinodes) form



  • A microwave source is placed in line with a reflecting plate and a small detector between the two
  • The reflector can be moved to and from the source to vary the stationary wave pattern formed
  • By moving the detector, it can pick up the minima (nodes) and maxima (antinodes) of the stationary wave pattern

 Stationary wave microwave, downloadable AS & A Level Physics revision notes

Using microwaves to demonstrate stationary waves


Air Columns

  • The formation of stationary waves inside an air column can be produced by sound waves
    • This is how musical instruments, such as clarinets and organs, work

  • This can be demonstrated by placing a fine powder inside the air column and a loudspeaker at the open end
  • At certain frequencies, the powder forms evenly spaced heaps along the tube, showing where there is zero disturbance as a result of the nodes of the stationary wave

Air column stationary waves, downloadable AS & A Level Physics revision notes

Stationary wave in an air column


  • In order to produce a stationary wave, there must be a minima (node) at one end and a maxima (antinode) at the end with the loudspeaker


Nodes and Antinodes

  • A stationary wave is made up nodes and antinodes
    • Nodes are where there is no vibration
    • Antinodes are where the vibrations are at their maximum amplitude

  • The nodes and antinodes do not move along the string. Nodes are fixed and antinodes only move in the vertical direction
    • Between nodes, all points along the stationary wave are in phase
    • The image below shows the nodes and antinodes on a snapshot of a stationary wave at a point in time

Nodes and antinodes, downloadable AS & A Level Physics revision notes 

  • L is the length of the string
  • 1 wavelength λ is only a portion of the length of the string


Worked example

A stretched string is used to demonstrate a stationary wave, as shown in the diagram.

WE - Nodes and Antinodes question image(1), downloadable AS & A Level Physics revision notes

Which row in the table correctly describes the length of L and the name of X and Y?

WE - Nodes and Antinodes question image(2), downloadable AS & A Level Physics revision notes


Worked example - nodes and antinodes (2), downloadable AS & A Level Physics revision notes

Exam Tip

Always refer back to the experiment or scenario in an exam question e.g. the wave produced by a loudspeaker reflects at the end of a tube. This reflected wave, with the same frequency, overlaps the initial wave to create a stationary wave.

Can't remember which is the node and which is the anti-node? Nodes occur at areas of NO Disturbance!

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Lindsay Gilmour

Author: Lindsay Gilmour

Lindsay graduated with First Class Honours from the University of Greenwich and earned her Science Communication MSc at Imperial College London. Now with many years’ experience as a Head of Physics and Examiner for A Level and IGCSE Physics (and Biology!), her love of communicating, educating and Physics has brought her to Save My Exams where she hopes to help as many students as possible on their next steps.