What is a microwave oven (or “microwave”) and how does it work?

A microwave oven is an electrical appliance that is used to quickly heat up food. The microwave oven works by emitting electromagnetic waves (also called radio waves) of a specific length (2.5 gigahertz). This specific wavelength allows the waves to penetrate into certain materials, such as fat and water, where the waves then put the atoms and molecules of these materials into motion. And because heat is nothing more than molecules and atoms in fast motion, the motion created in fats and in water by the microwaves heats up the food into which the microwaves penetrate. Because microwaves are absorbed by water and fats but not by other materials such as plastic, paper or metal, microwaves heat just the food, and not the container. Metal in fact repels electromagnetic waves, so that metal food vessels can prevent food from heating up and may even cause sparks in the microwave. Microwave ovens in fact use metal patches in their interiors, causing the electromagnetic waves to be repelled ...  more