Microwaves

Microwaves and the microwave oven

Microwaves are photons. (a photon is an amount of light energy)
They are like radio waves

Microwave energy is produced inside machines that convert (change) the
radio waves into microwave energy

Microwaves are used in wireless internet and phone networks.

Radar uses microwaves.

How a microwave oven works
In a microwave oven there is a piece of machinery called a magnetron which produces microwaves. The microwaves are absorbed by the water, fats and sugars in the food placed inside the oven. Other microwaves reflect off the walls into the food. When the microwaves are absorbed, the molecules in the food are ‘excited’ and move rapidly. This movement is called atomic motion and it creates heat. The temperature rises and the food cooks. Microwaves cook food very quickly and evenly. The walls and door of the oven are insulated to stop heat escaping from the oven. The timer and heat setting buttons on the outside of the oven control the amount of heat going into the food.

The first microwave oven
In 1946, engineer Dr. Percy Spencer was testing a new vacuum tube called
a magnetron when he discovered that the candy bar in his pocket had melted. This intrigued Dr. Spencer, so he tried another experiment. This time he placed some popcorn kernels near the tube and watched as the popcorn sputtered, crackled and popped all over his laboratory. Dr. Spencer experimented with other food including eggs.

Later he made a metal box with an opening into which he fed microwave power. The energy entering the box was unable to escape and the temperature rose quickly. This was the first microwave oven.
The first microwave oven was patented in 1954, but was too big to be used in people’s homes. In the
1970s, smaller, efficient microwave ovens were developed for use in homes and restaurants.

What did the Microwave oven replace?
Conventional ovens were heated with either gas flame or an electric heating element. The oven surfaces become hot and this cooks the food placed inside the oven. The heat penetrates the food from the outside towards the middle. The hot air dries and cooks the outside of the food more quickly, but the middle can be left less well cooked. In conventional ovens, a lot of the heat gets lost through the door and the walls, unlike microwave ovens.

Here’s a link for more about the microwave oven and about the safety of microwaves.
http://en.wikibooks.org/wiki/Wikijunior:How_Things_Work/Microwave_oven

If you use any of this information in your own work, acknowledge this source in your bibliography like this:
Thomas, Ron & Sydenham, Shirley. Microwaves and the microwave oven [Online] www.kidcyber.com.au (2011)

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