The microwave is the short name for a device that heats food by passing electromagnetic radiation through it. It’s a form of non-ionizing electromagnetic radiation with wavelengths of about one-tenth that of radio waves and less than that of infrared and X-rays. The frequency of microwaves is in the ISM (industrial, scientific and medical) band, which means it doesn’t require a license to operate and doesn’t interfere with other vital radio services.
Microwaves are produced inside a microwave oven by a device called a cavity magnetron, which is actually a high-voltage motor that outputs energy in the form of electromagnetic radiation. The microwaves are tuned to resonance with water molecules, and they emit energy as they move through the appliance. The microwave oven’s safety features shut off the device if the door is opened, which is how it avoids the type of radiation damage that can occur with higher-frequency devices such as radar antennas.
In addition to cooking, microwaves are used in point-to-point telecommunications systems that transmit voice, data and video in analog and digital formats. They’re also used in a variety of industrial processes, such as food and chemical processing.
Some researchers use microwave radiation to study extraterrestrial life, although the attenuation of atmosphere at these frequencies makes this difficult from Earth. Direct exposure to microwaves can cause physical burns, particularly in areas like the eyes and testes that lack blood flow to carry away the heat. The Food and Drug Administration regulates the safety of microwave ovens.