How Does a Microwave Work?

For many people, the humble microwave is one of modern life’s greatest conveniences. You load in a frozen dinner or burrito and push a few buttons, and within minutes it’s all done for you. But just how does it work?

The microwave oven’s magnetron oscillator feeds a beam of electromagnetic radiation into a closed metal cavity, where it interacts with the food to heat it quickly and evenly. It can also be used to warm liquids, although the outer layers may not absorb the microwave energy as well. For this reason, it’s important to stir them often while heating and to use a microwave-safe container.

Microwaves have a large information-carrying capacity (bandwidth) and can travel over long distances without being affected by atmosphere. They’re used for communication between distant cities, as well as for satellite-to-ground relay links. In the 1940s, experimental 3.3 GHz transmitters at Westinghouse labs were used to transmit voice and video across the English Channel using bidirectional microwave beams.

The microwave wavelength is very small, compared to infrared radiation and radio waves. The prefix “microwave” comes from the fact that the radiation is in the microwave frequency range, which lies between radio waves and far infrared radiation on the electromagnetic spectrum. This range is sometimes referred to as the SHF (super high frequency) or UHF (ultra high frequency) radio band, in addition to being called millimeter wave in some contexts. Like all electromagnetic radiation, microwaves can cause harm to living tissue if they’re absorbed by it in large enough amounts. But microwave ovens are designed with multiple safety features to protect against this, and long-term rodent studies have found no carcinogenic effects from 2.45 GHz microwave radiation.