GCSE PHYSICS - What is the Electromagnetic Spectrum? - Frequency - Wavelength - Energy - Intensity

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What is the Electromagnetic Spectrum?

Electromagnetic waves can have wavelengths which
range from several thousand metres to
less than one million millionth of a metre.
The waves are divided into wavelength ranges
according to the wave's effect or uses.

This is called the electromagnetic spectrum.

You need to know the order of the regions shown above
and that radio waves have the longest wavelength
(up to 10⁴ metres and beyond) and that gamma rays
have the shortest wavelength (down to 10^-15 metres).

How do the Wavelength, Frequency and Energy Change?

As the wavelength decreases, the frequency increases.
Wavelength is inversely proportional to frequency
(if the speed of the wave is constant).
Radio waves have the smallest frequency
and gamma rays have the largest frequency.

The amount of energy that the wave has
increases as the frequency increases
(and the energy of each photon increases).
Radio waves have the smallest amount of energy
and gamma rays have the largest amount of energy.

What is the Intensity of Electromagnetic Radiation?

The intensity of a beam of electromagnetic radiation
is a measure of the amount of energy hitting
each square metre of surface every second. The actual
amount of energy depends on the energy of each photon
as well as the number of photons hitting the surface.

The intensity of electromagnetic radiation decreases the further it
travels because it spreads out over a bigger surface area
and some electromagnetic radiation is absorbed by the air.

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