How Does a Microwave Work Inside?

The Science

Microwaves use a process called dielectric heating, or RF heating. This method uses electromagnetic radiation, in the form of radio waves, to induce molecular rotation in specific, susceptible molecules. Molecules that contain this polar quality will align themselves when stimulated. It is this rotation of excited molecules that produces friction heat, warming the item. The most polar molecule typically found in foods is water, although fats and sugars also rotate when stimulated by radio waves. Unique to dielectric heating is the simultaneous rotation of all molecules subject to the electromagnetic radiation, producing the even heating typical of a microwave oven.

Mechanics

Conducting at frequencies slightly above radio but below the visible spectrum, microwave ovens achieve electromagnetic radiation through three basic components. The transformer changes electrical power from a socket into usable energy for the microwave's components. This energy powers a magnetron, which produces RF waves through the interaction of a powerful magnet and an electrically-heated cathode. This energy, which radiates outward, is directed downward by a pipe called an electromagnetic waveguide. These three components form the entire operational capacity of a microwave.

Containment and Use

The three basic components are contained within the microwave's enclosure, which is a conducting Faraday cage that dissipates energy along the inner surface. Contained in its Faraday cage, the microwave oven's basic components produce a single consistent frequency. Since there is no variability within the movement of the magnetron, different power levels actually reflect intervals of applied radiation. The magnetron is either on or off, firing continuously or in short bursts. This simplicity means that all of the buttons on a microwave's face only affect the on or off state of the magnetron, making the control aspect of the microwave surprisingly simple.