Electromagnetic (EM) Waves (Edexcel IGCSE Physics (Modular))
Revision Note
Written by: Katie M
Reviewed by: Caroline Carroll
Properties of em waves
Light is part of a continuous electromagnetic spectrum that consists of the following types of radiation:
radio
microwave
infrared
visible
ultraviolet
x-ray
gamma ray
All waves in the electromagnetic spectrum share the following properties:
They are all transverse
They can all travel through free space (a vacuum)
They all travel at the same speed in free space
The EM spectrum
The types of radiation found in the electromagnetic spectrum have a specific order based on their wavelength (and frequency)
This order listed above has:
Radio waves at the top because they have the longest wavelength (and highest frequency)
Gamma rays at the bottom because they have the shortest wavelength (and lowest frequency)
Wavelength and frequency are inversely proportional to each other:
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)
This is explained by the Wave equation
The types of radiation in the EM spectrum from longest to shortest wavelength
Visible light is just one small part of a much bigger spectrum: The electromagnetic spectrum
Visible Spectrum
Visible light is the only part of the EM spectrum detectable by the human eye
However, it is only a very small part of the whole electromagnetic spectrum
In the natural world, many animals, such as birds, bees and certain fish, can perceive beyond visible light and use infra-red and UV wavelengths of light to see
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)
Violet has the shortest wavelength (and the highest frequency)
The colours of the visible spectrum
The colours of the visible spectrum: red has the longest wavelength; violet has the shortest
Examiner Tips and Tricks
See if you can make up a mnemonic to help you remember the order of the colours of visible light in 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!
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)
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