Electromagnetic Waves (CIE IGCSE Physics)
Revision Note
Author
Katie MExpertise
Physics
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 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
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
The Speed of Electromagnetic Waves
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
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