The Electromagnetic Spectrum

Electromagnetic Waves

Consist of self-sustaining electric and magnetic fields
Light can be pictured as a combination of transverse electric and magnetic waves moving through space
Light waves are the result of electrons moving within atoms- an oscillating chrage which sets up an electric field and therefore a magnetic field
Radio waves are created by electrons moving in wires
EM waves travel through a vacuum at 3 X 10^8 ms-1
They are part of big "family" of waves with varying wavelengths

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Highest frequency, longest wavelength
Used in communications
You can easily generate radio waves of a particular frequency using an alternating current and an aerial
Will not interfere with waves of another frequency- therefore many radio stations can broadcast in one area
The Ionosphere, an electrically charged layer in the atmosphere, reflects and refracts radio waves
Waves would be lost by the curvature of the earth but this prevents this from happening- reflected back down. This is used in the long distance broadcasting of radio signals.
But it means radio communications with satellites are not possible with the frequencies affected

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Higher freq, shorter wavelength that radio waves
Used for communications with satellites as they are not reflected by the ionosphere
Shorter wavelength so shorter aerial needed for transmitting/receiving
Ideal for mobile phones and other handheld communication devices

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Higher freq, shorter wavelength than microwaves
Travels through glass in a very simlar way to light
Total internal reflection is used to carry it along optic fibres
Used for wire communications in this way to increase the range of frequencies used (alongside visible light) and therefore maximise the amount of information that can be transmitted at one time
Heat radiation is also carried primarily by infrared rays
Toasters and grills sue infrared to cook food

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Wavelength 400nm-700nm
Very small section of the spectrum
Apart from a large range of radio waves, only wavelengths that naturally occurs at the surface of the earth
Sine birds and insects can also see in a range of UV wavelengths
Gives them richer, more detailed vision

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