Microwave Ovens!!!
One of the most revolutionary kitchen tools we have today was accidentally discovered and then invented in the 1940s and ’50s. The microwave oven, whose origins has nothing to do with cooking, dates back to World War II. According to IdeaFinder.com:
During World War II, two scientists invented the magnetron, a tube that produces microwaves. Installing magnetrons in Britain’s radar system, the microwaves were able to spot Nazi warplanes on their way to bomb the British Isles…. The idea of using microwave energy to cook food was accidentally discovered by Percy LeBaron Spencer of the Raytheon Company when he found that radar waves had melted a candy bar in his pocket. Experiments showed that microwave heating could raise the internal temperature of many foods far more rapidly than a conventional oven.
So, what exactly is a microwave, and are microwave ovens safe? We’ll need to consider the electromagnetic spectrum, something you’ve probably seen in your high school physics and chemistry classes.
The Electromagnetic Spectrum
Put simply, a “micro”-wave is a “small” wave that is on the order of 1 centimeter, not on the order of 1 micrometer, as the name would suggest. That is, these waves have wavelengths of about 1 centimeter. (A centimeter, or cm, is 1E-2 m.) When we compare this with visible light, which is on the order between 1E-6 and 1E-7, we see that microwaves are longer than visible light. If we remember that speed of light = (frequency of the wave)*(wavelength of the wave), where the speed of light is about 2.9979E8 m/s, then we can see that frequency is inversely proportional to the wavelength. What this means is microwaves travel at a lower frequency than visible light. (Frequency is measured in cycles per second, or Hertz.)
Again, from IdeaFinder.com:
[Microwaves] are found in the non-ionizing portion of the energy spectrum, between radio waves and visible light. “Non-ionizing” means that microwaves do not detach charged particles and produce atoms with an unbalanced plus or minus charge. Microwaves can therefore safely produce heat and not cause food to become radioactive.
Now, let’s take a look at a few practical things about microwave ovens, like why radiation doesn’t escape into the kitchen, or is it safe to stop the microwave and reach in to grab the piping hot HotPocket about eat it right away? If you notice that there is a metal mesh screen in the door of the microwave. The side of the holes, on the order of half a centimeter or so, allows the physically smaller visible light waves to pass through but prevents the “larger” microwaves from leaving the microwave oven (remember that light waves are orders of magnitude smaller than microwaves). Also, you don’t need to worry about residual microwave radiation from the microwave oven because these waves always travel at the speed of light and will have been absorbed into your food long before it gets a chance to escape and hit you in the face.
More information on the history of the microwave oven can be found at Gallawa.com. Image from ScienceProg.
