The Electromagnetic Spectrum (Edexcel GCSE Physics: Combined Science)

Revision Note

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Katie M

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The EM Spectrum

  • The main groupings of the continuous electromagnetic (EM) spectrum are:
    • Radio waves
    • Microwaves
    • Infrared
    • Visible (red, orange, yellow, green, blue, indigo, violet)
    • Ultraviolet
    • X-rays
    • Gamma rays

Examiner Tip

See if you can make up a mnemonic to help you remember the EM spectrum!One possibility is:

Raging Martians Invaded Venus Using X-ray Guns

To remember the colours of the visible spectrum you could remember either:
  • The name “Roy G. Biv”
  • Or the saying “Richard Of York Gave Battle In Vain”

Colours of the spectrum, IGCSE & GCSE Physics revision notes

You could even combine both to have a mega mnemonic:

Raging Martians Invaded Roy G. Biv Using X-ray Guns!

EM Wavelength & Frequency

  • 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

Examiner Tip

The electromagnetic spectrum is usually given in order of decreasing wavelength and increasing frequency i.e. from radio waves to gamma wavesRemember:

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

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

  • Each colour within the visible light spectrum corresponds to a narrow band of wavelength and frequency
  • 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)

Wavelength of spectrum, IGCSE & GCSE Physics revision notes

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

  • Wavelength and frequency are inversely proportional, this means that:
    • An increase in wavelength is a decrease in frequency (towards the red end of the spectrum)
    • decrease in wavelength is an increase in frequency (towards the violet end of the spectrum)

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Katie M

Author: Katie M

Expertise: Physics

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.