Electromagnetic (EM) Waves (AQA GCSE Physics)

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)

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)

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