Stationary Waves (OCR AS Physics) : Revision Note

Katie M

Author

Katie M

Last updated

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 waves store energy, unlike progressive waves which transfer energy

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

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

  • Stationary waves can be represented by various mediums

Stretched String

  • 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 a length of string under tension fixed at one end and vibrations made by an oscillator:

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

Microwaves

  • 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

Examiner Tips and Tricks

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.

Graphical Representation of a Stationary Wave

  • A stationary wave is formed when two waves travelling in opposite directions along the same line overlap with each other

  • The waves must have:

    • The same speed

    • The same frequency (or wavelength)

    • A similar amplitude

  • As a result of superposition, a resultant wave is produced

Formation of stationary waves (1), downloadable AS & A Level Physics revision notes

Nodes and antinodes are a result of destructive and constructive interference respectively

  • A stationary wave is made up of nodes and antinodes

  • At the nodes:

    • The waves are in anti-phase meaning destructive interference occurs

    • This causes the two waves to cancel each other out and there is no vibration

  • At the antinodes:

    • The waves are in phase meaning constructive interference occurs

    • This causes the waves to add together and the vibration is at maximum amplitude

👀 You've read 1 of your 5 free revision notes this week
An illustration of students holding their exam resultsUnlock more revision notes. It's free!

By signing up you agree to our Terms and Privacy Policy.

Already have an account? Log in

Did this page help you?

Katie M

Author: Katie M

Expertise: Physics Content Creator

Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential.

Download notes on Stationary Waves