Contains the full lesson along with a supporting toolkit, including teachers’ notes.
Each time we use a mobile phone, watch TV or listen to a radio programme we are making use of the electromagnetic spectrum. More correctly, we are using a subset of that spectrum called the radio spectrum. In this lesson we look at the radio spectrum and the communication services that depend on it. We also discuss the role of ComReg (see panel) in managing the use of the spectrum and the need for such management.
What is the electromagnetic spectrum?
When electrons move symmetrically back and forth or oscillate, their electric and magnetic fields change together, forming an electromagnetic wave. Although it may not be obvious, visible light, radio waves, microwaves and x-rays are all electromagnetic waves. These waves travel through space at the speed of light, usually denoted by the symbol c. This symbol stands for ‘constant’. The speed of light is constant at 299,792,458 metres per second (approximately 3x108 m/s).
Even though all the waves travel at the same speed, they are not the same. They have different frequencies and different wavelengths. In fact, if the frequency is different, then the wavelength must also be different since the frequency multiplied by the wavelength gives the speed which, in this case, is a constant. This is normally shown by the equation
f x λ = c.
The range of frequencies involved is called the electromagnetic spectrum.
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Its remit covers all kinds of transmission networks including: