How Does the Microwave Work?
If you’re new to microwave cooking, take the time to learn how your oven works.
The heart of the microwave is the magnetron tube, which converts ordinary household electricity into high-frequency microwaves. When they reach the oven cavity, the microwaves are distributed by a metal-bladed stirrer fan. Depending upon the materials they contact, the waves act in different ways: they’ll reflect from some substances, simply pass through others, and be absorbed by still others.
Because metal reflects microwaves, the basic wall material and stirrer fan are made of metal. Glass, pottery, paper, and plastic allow microwaves to pass through, so these are used for cooking containers and coverings. Containers can pick up heat from the food itself, though—so if a dish has been in the oven for a fair amount of time, be sure to handle it with potholders.
The water, fat, and sugar in foods absorb microwaves, which in turn cause the molecules in the food to vibrate rapidly. That leads to friction, heat, and ultimately cooking. Since microwaves generally penetrate to a depth of only 3/4 to 1 1/2 inches, the center of a large mass, such as a roast or a good-sized casserole, will be cooked not by microwave energy, but by the surrounding heat as it’s conducted inward.
The air in the oven isn’t affected by microwaves, so it usually stays cool. But be aware that quite a lot of steam can become trapped inside covered cooking containers. To avoid steam burns, always be very careful when uncovering dishes; remove the lids so that any steam will escape away from you.
