Glossary: microwave oven

A microwave oven cooks with high-frequency radio waves that cause food molecules to vibrate, creating friction that heats and cooks the food. Microwaves travel so fast (and therefore cook food quickly) because they're extremely short. Nonmetal containers are used in these special ovens because microwaves pass through them (unlike metal), thereby cooking the food from all angles (top, bottom and sides) at once. The fact that the waves pass through glass and ceramics means that the containers stay relatively cool while the food they contain becomes quite hot. The exception is when, during long cooking periods, the food can make the container very hot. Ideally, containers and products like paper towels and paper plates suitable for microwave cooking should be labeled 'microwave safe.'

From THE NEW FOOD LOVERS COMPANION, Fourth edition by Sharon Tyler Herbst and Ron Herbst. Copyright © 2007, 2001, 1995, 1990 by Barron's Educational Series, Inc.