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
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
Exam 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
