The Basics of the Microwave

The microwave is a handy household appliance that heats food and liquids quickly and conveniently. It can save energy, and it cooks food better than conventional ovens do by preserving the appearance, flavor, and nutritional composition of foods [1].

The basic concept behind the microwave is pretty simple. Microwaves are electromagnetic waves with wavelengths from about a millimeter to one meter and frequencies between 300 megahertz (MHz) and 3 gigahertz (GHz).

As they travel through the air or through food, the electromagnetic waves bounce around inside the cooking cavity, creating vibrations in the molecules of whatever they encounter. The friction between these molecules is what creates the heat.

These waves lose their energy the farther they penetrate into your food, which is why the inner part of a joint of meat will be cooked by conduction and the outer layer by radiation. That’s also why you shouldn’t put metal objects in your microwave: it can induce an electric current that runs between bits of metal, which can eventually cause them to arc together in a plasma of ionized gas and start a fire.

The control panel lies beside the door of a modern microwave, and it allows you to set various cooking modes like defrosting or quick heating. Most microwaves use a magnetron to generate the microwaves that cook your food. You can usually locate the magnetron by looking for a plastic panel inside the cooking cavity that covers it. The magnetron emits microwave radiation, and the waves travel through a wave guide or turntable before they reach your food.