Science of Microwave Heating :: microwave oven

The microwave oven, a tool that we use often in our busy lives to heat up foods when we just don't have the time or patience for a conventional oven to do its work. How does this device work? It's pretty simple if we use the basics of physics to explain it. Vibrations from the high frequency radio waves cause the water and fat cells in food to generate heat through friction of the molecules. An example of this using a turkey shows the molecules positive and negative particles acting through these vibrations to cause friction. J. Carlton Gallawa -- http://www.gallawa.com/microtech/howcook.html "In microwave cooking, the radio waves penetrate the food and excite water and fat molecules pretty much evenly throughout the food. There is no "heat having to migrate toward the interior by conduction". There is heat everywhere all at once because the molecules are all excited together. There are limits of course. Radio waves penetrate unevenly in thick pieces of food (they don't make it all the way to the middle), and there are also "hot spots" caused by wave interference, but you get the idea. The whole heating process is different because you are "exciting atoms" rather than "conducting heat"." -- Howstuffworks.com From Wikipedia.org: "Microwaves, also known as Super High Frequency (SHF) signals, have wavelengths approximately in the range of 30 cm (1 GHz) to 1 mm (300 GHz)." and "A microwave oven uses a magnetron microwave generator to produce microwaves at a frequency of approximately 2.4 GHz for the purpose of cooking food. Microwaves cook food by causing molecules of water and other compounds to vibrate. The vibration creates heat which warms the food. Since organic matter is made up primarily of water, food is easily cooked by this method." From http://www.gallawa.com/microtech/howcook.html: "Microwaves possess three basic characteristics: * Just as sunlight shines through a window, microwaves pass right through some materials. Materials such as glass, paper, and plastic are transparent to and generally unaffected by microwaves. * Microwaves are reflected by metal surfaces, much as a ball would bounce off a wall. The metal walls of the cooking space actually form a cavity resonator. In other words, the enclosure is designed to resonate the microwaves as they are radiated from the magnetron tube. The principle of resonance may be illustrated using sound waves. When a piano key is struck, it produces sound vibrations or sound waves. Sometimes a note is played on a piano, and an object across the room, perhaps a wineglass, can be heard vibrating and producing the same sound.