AQA GCSE Physics contents

Unit 6 · Waves

Types of Electromagnetic Waves

2 min read · part of the full Exam Guide

The electromagnetic spectrum

  • Electromagnetic waves are transverse waves that transfer energy from the source of the waves to an absorber
  • They do not need a medium: they can travel through a vacuum
  • Electromagnetic waves form a continuous spectrum, and all types travel at the same velocity through a vacuum (space) or air: 3.0×1083.0 \times 10^8 m/s
  • The waves are grouped by their wavelength and frequency. From long wavelength (low frequency) to short wavelength (high frequency):
Group Typical wavelength Notes
radio waves 1 m to 1000 m or more longest wavelength, lowest frequency
microwaves 1 mm to 1 m
infrared 10−610^{-6} m to 10−310^{-3} m emitted by all warm objects
visible light about 4×10−74 \times 10^{-7} m (violet) to 7×10−77 \times 10^{-7} m (red) the only part our eyes detect
ultraviolet 10−810^{-8} m to 4×10−74 \times 10^{-7} m
X-rays 10−1210^{-12} m to 10−810^{-8} m ionising
gamma rays below 10−1210^{-12} m shortest wavelength, highest frequency; ionising
  • The order can be remembered from the visible light colours: red (long wavelength) to violet (short wavelength), with infrared beyond red and ultraviolet beyond violet
  • Our eyes only detect visible light, a limited range of the spectrum

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electromagnetic spectrumradiomicroinfraredvisibleultravioletX-raysgammafrequency INCREASES → energy INCREASES← wavelength INCREASESredorangeyellowgreenblueindigovioletvisible light, expandedAll electromagnetic waves are TRANSVERSE, all travel at the same speed in a vacuum (3 × 10⁸ m/s),and all transfer energy from a source to an absorber.radio — TV and radio broadcasting microwaves — cooking, satellite communicationinfrared — heaters, remote controls, thermal imaging visible — seeing, fibre opticsultraviolet — energy-efficient lamps, sun tanning X-rays — medical imaginggamma — sterilising, treating cancerThe higher the frequency, the more energy each wave carries — and the more dangerous it is.UV can cause skin cancer; X-rays and gamma rays are ionising and can damage DNA.
The electromagnetic spectrum as a horizontal band from radio waves on the left to gamma rays on the right, with wavelength decreasing and frequency increasing along the arrows; the visible light section expanded to show red through to violet

Full Exam Guide

The rest of this topic is in the full Exam Guide

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In the full topic

  • The electromagnetic spectrum
  • Energy transfer by electromagnetic waves
  • Speed, frequency and wavelength
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