Electromagnetic (EM) Waves (Edexcel IGCSE Physics)

Properties of EM waves

• Light is part of a continuous electromagnetic spectrum that consists of the following types of radiation:

  • radio

  • microwave

  • infrared

  • visible

  • ultraviolet

  • x-ray

  • gamma ray

• All waves in the electromagnetic spectrum share the following properties:

  • They are all transverse

  • They can all travel through free space (a vacuum)

  • They all travel at the same speed in free space

The EM spectrum

• The types of radiation found in the electromagnetic spectrum have a specific order based on their wavelength (and frequency)

• This order listed above has:

  • Radio waves at the top because they have the longest wavelength (and lowest frequency)

  • Gamma rays at the bottom because they have the shortest wavelength (and highest frequency)

• Wavelength and frequency are inversely proportional to each other:

  • An increase in wavelength is a decrease in frequency (towards the red end of the spectrum)

  • A decrease in wavelength is an increase in frequency (towards the violet end of the spectrum)

  • This is explained by the Wave equation

The types of radiation in the EM spectrum from longest to shortest wavelength

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

Visible Spectrum

• Visible light is the only part of the EM spectrum detectable by the human eye

  • However, it is only a very small part of the whole electromagnetic spectrum

  • In the natural world, many animals, such as birds, bees and certain fish, can perceive beyond visible light and use infra-red and UV wavelengths of light to see

• 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)

  • Violet has the shortest wavelength (and the highest frequency)

The colours of the visible spectrum

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