Radio frequency fields are a form of low-energy electromagnetic (EM) field – energy transmitted as waves through space. EM fields surround us all the time. They occur naturally and have artificial sources.
EM fields are created whenever an electric current flows. In nature, they are created by lightning and also occur in the human nervous system. Light from the sun is a form of EM field. They are also created whenever an electrical appliance is connected to the mains supply, including many in daily use such as refrigerators, hairdryers and computers.
Many electrical appliances don’t just create EM fields – they rely on them to work. Television, radio, cordless phones, remote control handsets, baby monitors and the communication systems used by emergency services all communicate using EM fields. So do wireless technologies such as WiFi, which is increasingly used by computer networks, to connect to the internet and to connect different electronic items.
There are many forms of EM fields operating at different frequencies. Frequency is related to wavelength – the distance between one wave and the next. The closer together the waves are, the higher the frequency will be.
Some extremely high-frequency EM waves carry so much energy they can cause molecules to change. Examples include the x-rays used for medical diagnosis and radiotherapy treatment. These are known as ionising fields. Lower frequency EM waves, such as those used by mobile phones and base stations, do not have enough energy to cause molecules to change. These are non-ionising fields. All types of EM field fall into these two categories.