What Is a Microwave?

A microwave is the smallest device that can generate electromagnetic waves of such a high frequency that they can affect molecular vibrations and cause heating. The waves are called radio waves, and they have a long wavelength, much longer than the short wave lengths of visible light or the shorter wavelengths of X-rays, which can directly bash molecules and break their bonds. But the long wavelengths of microwaves can only penetrate into and heat water molecules, which are essentially hydrogen atoms.

Microwaves also create an electric current in metal objects (which is why they’re not allowed to work when the door is open). Depending on the metal object, the induced current can either make it through the food and cause melting or arcing, or it can find the easiest path between two bits of metal like the tines of a fork and start an electrical fire. This is the reason that, despite all those YouTube videos of people putting CDs or metal spoons in their microwaves to see what happens, it’s a very bad idea and a fire hazard.

While many of us rely on our microwaves to reheat leftovers and cook things like a baked potato or popcorn, the best models have features that make the appliance even more useful. For instance, you can set a timer by dialing in a number instead of pressing buttons to choose from preset functions designed for cooking items such as vegetables, potatoes and frozen foods. Some microwaves come with grilling and steaming capabilities, but those options generally add to the price of the unit.