Electromagnetic Waves (Cambridge O Level Physics)

Revision Note

Test yourself
Leander

Author

Leander

Last updated

Electromagnetic Waves

  • The electromagnetic spectrum is arranged in a specific order based on the wavelengths or frequencies
  • The main groupings of the continuous electromagnetic (EM) spectrum in order of increasing frequency and decreasing wavelength 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)

The Spectrum of Electromagnetic Waves

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

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

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

Remember:

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

Properties of Electromagnetic 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

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

The Speed of Electromagnetic Waves

  • 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

You've read 0 of your 10 free revision notes

Unlock more, it's free!

Join the 100,000+ Students that ❤️ Save My Exams

the (exam) results speak for themselves:

Did this page help you?

Leander

Author: Leander

Expertise: Physics

Leander graduated with First-class honours in Science and Education from Sheffield Hallam University. She won the prestigious Lord Robert Winston Solomon Lipson Prize in recognition of her dedication to science and teaching excellence. After teaching and tutoring both science and maths students, Leander now brings this passion for helping young people reach their potential to her work at SME.