A microwave oven uses an electronic device, the magnetron, to convert electrical energy into high-speed waves. These are deflected off the oven's metal walls directly into food to a depth of about 4 cm. These microwaves are then absorbed by molecules of moisture in the food, causing them to vibrate rapidly, which creates intense cooking heat. With larger pieces of food, the center is cooked by conduction, in the same way as in an ordinary oven.
Microwaves pass through china, glass, paper, pottery and some plastics, but metal deflects the microwaves so metal containers are not suitable to use.
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