The Electromagnetic Spectrum

This lesson covers the electromagnetic (EM) spectrum — the continuous range of electromagnetic waves from radio waves to gamma rays — as required by the AQA GCSE Physics specification (4.6.2). You need to know the order of the EM spectrum, the properties shared by all EM waves, and how wavelength and frequency change across the spectrum.

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What Are Electromagnetic Waves?

Electromagnetic (EM) waves are transverse waves that transfer energy from one place to another. Unlike sound waves, EM waves do not need a medium — they can travel through a vacuum (empty space).

Key properties of all EM waves:

• They are all transverse waves.
• They all travel at the same speed in a vacuum: 3 x 10^8 m/s (the speed of light).
• They can all travel through a vacuum.
• They all transfer energy.
• They can all be reflected, refracted, and absorbed.

Exam Tip: All electromagnetic waves travel at the same speed in a vacuum (3 x 10^8 m/s). This is a key fact that examiners love to test. The speed only changes when EM waves enter a medium (e.g. glass or water), where they slow down.

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