Electromagnetic Waves (Cambridge International IGCSE Physics)

Spec point — 3.3.1 · Know the main regions of the electromagnetic spectrum in order of frequency and in order of wavelength

Electromagnetic waves

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

  • Regions with a long wavelength have a low frequency and vice versa

• The main regions of the continuous electromagnetic (EM) spectrum from longest to shortest wavelength are:

  • radio waves
  • microwaves
  • infrared
  • visible (red, orange, yellow, green, blue, indigo, violet)
  • ultraviolet
  • X-rays
  • gamma rays

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

Exam Hint 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

Spec point — 3.3.1 · Know that all electromagnetic waves travel at the same high speed in a vacuum

• All electromagnetic waves travel at the same high speed in a vacuum
• Electromagnetic waves are defined as:

Transverse waves that transfer energy from the source of the waves to an absorber

The speed of electromagnetic waves

Spec point — 3.3.1 · Know that the speed of electromagnetic waves in a vacuum is 3.0 × 10^8m/s and is approximately the same in air

Extended Tier Only

• The speed of electromagnetic waves in a vacuum is

$3.0\times10^{8}m/s$

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