Resonance (Edexcel International A Level Physics)

Revision Note

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Ann H


Ann H




  • The frequency of forced oscillations is referred to as the driving frequency, f, or the frequency of the applied force
  • All oscillating systems have a natural frequency, f0, this is defined as the frequency of an oscillation when the oscillating system is allowed to oscillate freely
    • Oscillating systems can exhibit a property known as resonance


  • When the driving frequency approaches the natural frequency of an oscillator, the system gains more energy from the driving force
    • Eventually, when they are equal, the oscillator vibrates with its maximum amplitude, this is resonance
  • Resonance is defined as:

When the frequency of the applied force to an oscillating system is equal to its natural frequency, the amplitude of the resulting oscillations increases significantly

  • For example, when a child is pushed on a swing:
    • The swing plus the child has a fixed natural frequency
    • A small push after each cycle increases the amplitude of the oscillations to swing the child higher. This frequency at which this push happens is the driving frequency
    • When the driving frequency is exactly equal to the natural frequency of the swing oscillations, resonance occurs
    • If the driving frequency does not quite match the natural frequency, the amplitude will increase but not to the same extent as when resonance is achieved
  • This is because, at resonance, energy is transferred from the driver to the oscillating system most efficiently
    • Therefore, at resonance, the system will be transferring the maximum kinetic energy possible

Resonance Effects

  • Resonance occurs for any forced oscillation where the frequency of the driving force is equal to the natural frequency of the oscillator
  • Examples include:
    • An organ pipe, where air resonates down an air column setting up a stationary wave in the pipe
    • Glass smashing from a high pitched sound wave at the right frequency
    • A radio tuned so that the electric circuit resonates at the same frequency as the specific broadcast

Stationary Wave Organ Resonance, downloadable AS & A Level Physics revision notes

Standing waves forming inside an organ pipe from resonance

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Ann H

Author: Ann H

Ann obtained her Maths and Physics degree from the University of Bath before completing her PGCE in Science and Maths teaching. She spent ten years teaching Maths and Physics to wonderful students from all around the world whilst living in China, Ethiopia and Nepal. Now based in beautiful Devon she is thrilled to be creating awesome Physics resources to make Physics more accessible and understandable for all students no matter their schooling or background.