radio waves

Radio waves are the type of electromagnetic wave with the longest wavelength and the lowest frequency. They are produced by alternating currents in long aerials called transmitters.

When absorbed by aerials on radios or televisions they produce an alternating currents with the same frequency as the oscillations.

They are used for communications. The radio waves are divided into set wave bands of different frequencies.

>3000 MHz = UHF (ultra high frequency) = televisions

300 - 3000 MHz = VHF (very high frequency) = FM and digital radio

30 - 300 MHz = HF/SW (high frequency/short wave) = Amateur radio (walkie talkies)

3 - 3000 MHz = MF/MW (medium frequency/ medium wave) = national radio

300 - 3000 kHz = LF/LW (low frequency/ long wave) =

international radio

The ionosphere is a layer of gas in the upper part of the atmosphere which reflects SW, MW and LW radio waves.

This means that these radio waves can be sent a long way round the Earth, even though the Earth is curved.

The ionosphere is more intense in the summer than the winter so it is possible to pick up radios waves from further away in summer than in winter.