Microwaves and radio waves
At the low-frequency end of the spectrum lie microwaves and, lowest of all, radio waves.
Microwaves
The electromagnetic waves with frequencies just below infrared are called microwaves. They are used in radar systems, in mobile phones and in microwave ovens.
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How a microwave oven cooks
Water and fat molecules can absorb microwaves and turn that energy into the kinetic energy of vibration — heat. That is the principle of the microwave oven. The microwaves in ovens and radar are produced by a device called a magnetron.
Microwaves can harm the body
Microwave ovens are built so their microwaves do not escape, but it is still wise not to stay close to one unnecessarily while it is running. It is also thought that heavy use of mobile phones may damage the brain.
Radio waves
Radio waves have the longest wavelength and lowest frequency in the spectrum, and are used for long-distance communication. They are produced by radio-wave oscillators, and sent out and received by antennas.
Information is carried by changing the amplitude or the frequency of the radio wave to match it.
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