The Electromagnetic Spectrum (Edexcel GCSE Combined Science) : Revision Note
The EM Spectrum
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
Examiner Tips and Tricks
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
To remember the colours of the visible spectrum you could remember either:
The name “Roy G. Biv”
Or the saying “Richard Of York Gave Battle In Vain”
You could even combine both to have a mega mnemonic:
Raging Martians Invaded Roy G. Biv Using X-ray Guns!
EM Wavelength & Frequency
The electromagnetic spectrum is arranged in a specific order based on the wavelengths or frequencies
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
Examiner Tips and Tricks
The electromagnetic spectrum is usually given in order of decreasing wavelength and increasing frequency i.e. from radio waves to gamma wavesRemember:
Radios are big (long wavelength)
Gamma rays are emitted from atoms which are very small (short wavelength)
Visible Light
Visible light is defined as the range of wavelengths which are visible to humans
Visible light is the only part of the spectrum detectable by the human eye
However, it only takes up 0.0035% of the whole electromagnetic spectrum
In the natural world, many animals, such as birds, bees and certain fish, are able to perceive beyond visible light and can see infra-red and UV wavelengths of light
Each colour within the visible light spectrum corresponds to a narrow band of wavelength and frequency
The different colours of waves correspond to different wavelengths:
Red has the longest wavelength (and the lowest frequency and energy)
Violet has the shortest wavelength (and the highest frequency and energy)
The colours of the visible spectrum: red has the longest wavelength; violet has the shortest
Wavelength and frequency are inversely proportional, this means that:
An increase in wavelength is a decrease in frequency (towards the red end of the spectrum)
A decrease in wavelength is an increase in frequency (towards the violet end of the spectrum)
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