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The Science Behind The Microwave


April 4, 2013

Most every kitchen has one and we rely on it pretty much daily. That "it" is a microwave. But, do you know how it works? How it cooks your food?

Microwaves take our food from frozen to edible in just a matter of minutes. For years, they have turned anyone into a cook with the press of a button. Dr. Lou Bloomfield, Physics Professor at UVa, explained exactly how a microwave makes our cold food hot. Please don't try this at home.

Dr. Bloomfield said, "It's cooking food using basically radio waves. Microwaves and radio waves are very close cousins. They're little ripples of electricity and magnetism related to the static cling you have when you pull stuff out of the dryer. These electric ripples are fluctuating back and forth very fast and they catch the attention of water molecules. As they go back and forth, they rub against each other in your food and the food gets hot."

To show that electricity is a part of the cooking process, Dr. Bloomfield broke a few rules by putting metal in a microwave. He started by putting a CD in the microwave and pressing start.

Dr. Bloomfield explained, "The microwave oven is just trying to heat something. It's sending out it's microwaves and it doesn't care where they go. So, if they happen to go into the very thin aluminum layer in a CD, fine. It destroys the CD."

Next, he microwaved a light bulb and still didn't cause any damage.

Dr. Bloomfield demonstrated, "Here's a conventional, incandescent light bulb with no frosting. So, you can see the filament. I'm going to put it in some water in a beaker and put it in the microwave oven. Electricity will begin to run through parts of that bulb and it will light up. There we go, the gas is now glowing. So, that's a bulb not connected to anything. It's sitting in a bucket of water and it's lit up like a Christmas tree. *POP* and now it blew up.

We've always heard that putting metal in a microwave will damage our beloved appliance. It turns out that not all metals don't hurt a microwave unless it's thin or pointy.

Dr. Bloomfield said, "A microwave is actually very robust. It's hard to damage the transmitter part of the microwave oven but there are things that can do it. A very thin piece of metal that can't carry electricity well can get red hot and start a fire. Something that has sharp ends, can shoot sparks out can also start fires so twist ties are a disaster. Thick things like a spoon you can get away with putting a spoon in the microwave oven."

Bloomfield also said that even though a microwave can ruin a CD and blow up a light bulb, it's still very safe for your food.

"Microwaves live inside a metal box. It's a mirror for microwaves. So they're just bouncing around inside the box cooking your food. The box is pretty safe and the food cooked by it is as safe as any food you cook. It's not wonderful cooking but it's good for warming food," said Bloomfield.

All in all, microwaves are a modern marvel that make out lives that much easier when it comes to fast cooking. Even though metal in a microwave isn't always bad, it's best to not press your luck.

Bloomfield concluded, "I wouldn't recommend you put anything metal ion the microwave oven, it's just taking a risk but, there are many things that won't cause much trouble."

He also said that staring at a microwave while it's cooking is also harmless.

Bloomfield stated, "These things are regulated so you just can't have much radiation coming out. It's probably less than your cell phone. You cell phone communicates through microwaves so you're holding a little microwave transmitter right by your head and as far as we can tell, that's safe too. There's no evidence that microwaves coming out of your cell phone cause injury so, microwave oven, even less."


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