Electromagnetic Waves (CIE IGCSE Physics)

• The electromagnetic spectrum is arranged in a specific order based on the wavelengths or frequencies
• 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

• 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

• 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

• The 7 types of electromagnetic waves together form a continuous spectrum

EXTENDED

• The speed of electromagnetic waves in a vacuum is

3.0 × 10⁸ m/s

• This is approximately the same speed as electromagnetic waves in air