AQA GCSE Physics

Revision Notes

6.2.1 Electromagnetic (EM) Waves

Properties of EM Waves

  • Electromagnetic waves are defined as:

Transverse waves that transfer energy from the source of the waves to an absorber

  • All electromagnetic waves share the following properties:
    • They are all transverse
    • They can all travel through a vacuum
    • They all travel at the same speed in a vacuum
  • There are 7 types of electromagnetic waves, which all together form a continuous spectrum

The EM Spectrum

  • The electromagnetic spectrum is arranged in a specific order based on the wavelengths or frequencies
  • This order is shown in the diagram below from longest wavelength (lowest frequency) to shortest wavelength (highest frequency)

EM spectrum diagram, downloadable AS & A Level Physics revision notes

Visible light is just one small part of a much bigger spectrum: The electromagnetic spectrum

  • The higher the frequency, the higher the energy of the radiation
  • Radiation with higher energy is:
    • Highly ionising
    • Harmful to cells and tissues causing cancer (e.g. UV, X-rays, Gamma rays)
  • Radiation with lower energy is:
    • Useful for communications
    • Less harmful to humans

Visible Light

  • Visible light is defined as the range of wavelengths which are visible to humans
  • Visible light is the only part of the spectrum detectable by the human eye
    • However, it only takes up 0.0035% of the whole electromagnetic spectrum
  • In the natural world, many animals, such as birds, bees and certain fish, are able to perceive beyond visible light and can see infra-red and UV wavelengths of light
  • The different colours of waves correspond to different wavelengths:
    • Red has the longest wavelength (and the lowest frequency and energy)
    • Violet has the shortest wavelength (and the highest frequency and energy)

Chemistry of Transition Elements - Visible Light Spectrum, downloadable AS & A Level Chemistry revision notes

Colours of the spectrum, IGCSE & GCSE Physics revision notes

The colours of the visible spectrum: red has the longest wavelength; violet has the shortest

Exam Tip

To remember the colours of the visible spectrum either remember:

  • The name “Roy G. Biv”
  • Or the saying “Richard Of York Gave Battle In Vain”

The electromagnetic spectrum is usually given in order of decreasing wavelength.

Remember:

  • Radios are big (long wavelength)
  • Gamma rays are emitted from atoms which are very small (short wavelength)

Author: Katie

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.
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