TOP-TECH: microwave oven

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| How does the microwave oven work? | What science made the microwave oven possible? | The future |

How does the microwave oven work?

Microwave ovens use radio waves at a specifically set frequency to agitate water molecules in food. As these water molecules get increasingly agitated they begin to vibrate at the atomic level and generate heat. This heat is what actually cooks food in the oven. Because all particles in the food are vibrating and generating heat at the same time, food cooked in the microwave cooks much more swiftly than food cooked in a conventional oven where heat must slowly travel from the outside surface of the food inward.

The same radio waves that cook your food pass harmlessly through plastics, glass, and ceramics. It is this characteristic that keeps plastic plates from melting and glasses from exploding. It is also this feature of microwaves that makes them so energy efficient; they heat only the food and nothing more.

Metals, on the other hand, reflect these radio waves, a characteristic very cleverly put to use in the walls of the microwave such that no waves escape and cook anyone in the kitchen!

All of the waves discussed so far are created inside a device called a magnetron. The magnetron pulls electrons (tiny negatively charged particles) off a fine heated wire and then uses magnets to rotate them around inside a vacuum (a space void of any other particles). As these electrons swirl around and around they generate radio waves that are then sent into the oven to cook food.

From J. Carlton Gallawa

What science made the microwave oven possible?


From J. Carlton Gallawa

Magnetron technology was not invented with the intention of giving the world a quick way to heat food. It was actually first fully developed for military radar systems. The switch from enemy detection to cooking came one day in 1946 when a radar system engineer named Percy Spencer was testing a new magnetron. He felt a strange tingling sensation and suddenly noticed that the candy bar in his pocket had melted. He then placed popcorn, eggs and other foods in front of the device and they all cooked - actually the egg exploded all over his friend's face! Needless to say culinary history was made.

The future

Many microwave oven models already use sensors to detect how well cooked the food inside them is and shut themselves down before anything gets overdone. And this trend of "intelligent" food preparation shows no sign of slowing down. Sharp Electronic has released prototype microwaves that can download heating instructions for specific dishes from the Internet and prepare them without the user ever having to enter cook times.

By Mathilde Wolpert, scientist @ESRF
Edited by
Matt Kaplan, Science writer

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