- The Washington Times - Thursday, March 6, 2003

Richard Berg is one of the millions of Americans who use a microwave oven to heat or cook food practically 365 days of the year.
Unlike most of those millions, however, Mr. Berg knows how the little metal box to some the greatest invention of the 20th century works.
"The idea is that the microwave, which is a very-high-frequency radio wave, penetrates the food and flip-flops the water [and fat] molecules, creating kinetic energy," says Mr. Berg, director of the Physics Lecture-Demonstration Facility at the University of Maryland,
"Material in this case food that has kinetic energy gets hot."
So, that means food in a microwave oven is heated when its building parts atoms and molecules are "excited" by the microwaves. This means food is heated from the inside and not from the outside, as it is in conventional ovens.
The main component of a microwave oven is the magnetron tube, which transforms electric energy into a rapidly moving electromagnetic field at a frequency of 2.45 gigahertz a microwave.
The microwave itself is not hot, which is why the air inside a microwave oven stays at room temperature while the food inside it can be a couple of hundred degrees.
In a conventional oven, the surface of the food for example the crust of a loaf of bread is heated first, after which the heat penetrates the bread. The bread bakes when the heat migrates or conducts throughout the dough.
The ability of microwaves to heat food has been known since World War II, when engineer Percy Le Baron Spencer while doing radar experiments for weapons manufacturer Raytheon noticed that a chocolate bar in his pocket melted, says Louis Bloomfield, professor of physics at the University of Virginia.
Radar (an acronym for radio detection and ranging) consists of radio waves that are about the same length as microwaves, which is why the radar melted the chocolate the same way microwaves would have, Mr. Bloomfield says.
Shortly after Mr. Spencer's discovery, microwave ovens began appearing in restaurant kitchens.
The early ones had only one setting. They were either on or off, Mr. Bloomfield says. Now microwave ovens come with bells and whistles, including multiple settings, but the basic technology is still the same, he says.
The frequency of the microwaves is the same 2.45 gigahertz whether the setting is on high, low or defrost. The reason it takes longer to heat something on the low setting is because for this setting, the microwaves are switched on and off intermittently.
"The defrost cycle is just a glorified version of that," Mr. Bloomfield says. "It's a cycle that shuts off the microwaves for a while, letting the heat diffuse through the food and moving it to the cooler spots."
Turntables also improve the ability of the microwave to evenly penetrate the food, he says.
• • •
Though people may say they are going to "nuke" their food in a microwave, nothing nuclear is involved.
"It's a common belief that microwaves have something to do with nuclear radiation, but there is nothing radioactive about them," Mr. Berg says. Hence, no danger of radiation.
Mr. Bloomfield agrees. Microwaves cannot change things on a chemical level. They only have thermal properties.
"Different radiations are different radiations," Mr. Bloomfield says. "The very short wavelengths like gamma and X-rays are dangerous to life. They can do chemical damage. You can get cancer if you're exposed to [ultraviolet] rays, but microwaves do thermal damage, not chemical."
"Microwaves cook the food granted, in a weird way but that's basically all they do," Mr. Bloomfield says.
If the microwaves leak from an oven, they are unlikely to be harmful to humans, but they can interfere with communication devices, such as cell phones and hand-held computers because those electronic devices use radio waves that are similar to microwaves, Mr. Bloomfield says.
If the leak is enormous if the oven's door is falling off its hinges a person standing close by might burn himself or herself, Mr. Bloomfield says.
"There are cases when someone tried to dry a cat and killed it," Mr. Berg says. "Just don't play with the dumb thing. Use it safely, and you'll be fine."
• • •
Microwaves usually don't affect containers in which the food is held, but there are times when sparks are seen jumping from metals inside the oven. This is because microwaves push on electric charges, and because metals contain electric charges, microwaves drive electric currents through them.
In a thin piece of metal, this current can cause heating and therefore fire. In a sharp piece of metal, the charges leap out in the form of sparks.
Thick and dull metals are not a problem, however.
Other containers, such as porcelain cups or plates, can get hot in a microwave oven, but the microwaves aren't heating them the hot food is.
Although microwave manufacturers continue to tweak their product, Mr. Bloomfield says microwave ovens are a very "mature product," and he does not believe they will change significantly in the future.
So, consumers simply have to learn what the metal boxes do well and what limitations they have.
Carla Hall, a chef instructor and owner of a catering business in Northwest, says she isn't a big fan of this great consumer invention.
"I can't stand using microwaves for cooking," Ms. Hall says. "You don't have much control, and it heats unevenly."
Ms. Hall uses microwave ovens to soften butter and melt chocolate, but that's about it.
Mr. Berg, on the other hand, calls the microwave "an enormous boon in our modern times when people don't have time to cook."
"I like to cook vegetables in the microwave oven," Mr. Berg says. "The neat thing is you can use the water in the vegetables, so you don't have to drain water off along with all the vitamins."
Ms. Hall acknowledges the practicality of the microwave but says she naturally doesn't share most people's wish to "get out of cooking a meal."
"I understand that they make life easier," Ms. Hall says, "but cooking is what I do for a living. It's what I love, and I'd rather take the time to get it right."

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