Microwaves - Electromagnetic waves

How often have you talked about heating up something in the microwave and used the term "nuke it"? That phrase has been used over the years and some have interpreted the phrase to imply that a device of nuclear proportions exists right there on their kitchen counter. Let's play a little word association game for a minute; we'll start at "nuclear". Ready? "Nuclear...atomic power plants...atom bomb... radiation...nuclear fallout". Scary? Yep! I’m also scared at where we ended up. Rest assured that your microwave oven is no where near capable of splitting any atoms and your home address will never be synonymous with Chernobyl!

I'll apologize in advance for the length of this section, but it is well worth thoroughly understanding.

In order to understand the difference between harmful and harmless electromagnetic waves, let's go back to high school physics and take a brief but important look at the electromagnetic spectrum. Firstly, let's consider the term "frequency" and outline the difference between low frequency and high frequency and the difference between the two.

Imagine sitting in a chair and having your friend sitting facing you 3 feet away. Your friend (although I'm not sure you'll call them your friend after this example) is shooting popcorn kernels at you through a straw, each of them traveling at the exact same speed. We will assume that your friend is an expert marksman with shooting kernels and will hit the exact same spot with every shot. He starts off by shooting one kernel every 30 seconds. No big deal - we have plenty of time in between each shot to recover and it is relatively painless. He increases the frequency of his shots to one every 10 seconds. Still, relatively harmless to us and we are beginning to feel superhuman in repelling the kernels. Now increase the frequency to one every second. After a little while at this frequency, it starts to become uncomfortable. While your superhuman abilities are decreasing, your friend's is increasing and he is now able to shoot them at you at 5 kernels per second. A few seconds in and we can start to feel the pain. Your body is no longer able to completely recover between kernel strikes and both pain and damage to your body is the result. Now, your friend truly enters superhuman mode and is shooting the kernels at 100 kernels per second. Ouch! There is now much damage being done to your body and the pain becomes unbearable. Can you imagine what the result would be if we increased the frequency to 1000 per second? Now we are beginning to understand the idea about frequency and how an increase in it can affect the damage it can impart. Even though the kernels were shot at the exact same speed, the time between them was cut so short that your body does not have time to recover between kernel impacts.

Although simplistic, the same principle of our above example can be applied to electromagnetic frequency. If we look at the full range of the electromagnetic spectrum and start at its lowest frequency, we see that at the lowest end we find AM radio waves. These waves have a frequency, that is, they are quite literally spaced apart at a distance roughly the width of a football field. Going up the spectrum (increasing in frequency) we next arrive at FM radio waves which have the frequency length about the width of a house. Next, we find our wavelength in question - microwaves. They are approximately the width of a baseball - still relatively large in comparison to what will come. Radar waves, those used by airports to track airplanes as they move through our skies are next. They are slightly larger than the size of the period found at the end of this sentence. Guess what is next in line in this example? That's right, YOU are! The electromagnetic wavelength that YOU emit is found within the infrared section. Certainly, the electromagnetic waves that you emit cause no harm to us! Of course, ask any ten year old boy and he will tell you that Aunt Gretchen’s hugs can be pretty painful to endure sometimes! Interestingly enough, those wavelengths are roughly the size of a human cell. How ironic.

Let's quickly think back to our kernel shooting friend. Can you imagine how shooting that kernel at you, at the same relative speed but over these decreasingly shorter distances is directly proportional to the damage it inflicts? Since the waves are moving at the same speed, but are closer together (since the distance they have to travel is shorter) they can penetrate through smaller openings and subsequently, they cause more damage. Still, with that said, none of the EM waves we have looked at so far have the ability to cause us harm, (save for Aunt Gretchen’s hugs) or change the molecular structure of matter they come into contact with.

Let's move one more step up this EM scale. Light bulbs. Certainly, you can agree that we are constantly struck by waves in this region. The size of these waves is roughly the width of a single bacterium - pretty darn small although still easy to imagine. If we jump up a couple of steps we come to X-rays. Yes, the kind of X-rays that you subject yourself to when getting an X-Ray at the Drs after you slip on the ice in the winter and break your arm! While relatively harmless, it is not advisable to over-expose yourself to these types of waves. They are about the size of the width of a molecule of water and far out of the visible range when using just the naked eye. Next we arrive at some real nasties - gamma rays. These guys are so small, that is, the wavelength is so short and squashed so close together that it's difficult to give you a practical reference as far as size goes. These are the guys that are going to harm you.

As illustrated by our example, the microwaves used in microwave ovens are sandwiched between the waves used for AM and FM radio and those used for radar equipment, television and radio communications. They are in the non-ionizing range of electromagnetic radiation. Non-ionizing radiation is very different from Ionizing radiation. Ionizing radiation is extraordinarily high in frequency (millions of trillions of cycles per second). It is, therefore, extremely powerful and penetrating. Even at low levels, ionizing radiation can damage the cells of living tissue. In fact, these dangerous rays have enough energy and intensity to actually change (ionize) the molecular structure of matter. In sufficient doses, ionizing radiation can cause genetic mutations. As outlined in our example, the ionizing range of frequencies includes X-rays, gamma rays, and cosmic rays. Ionizing radiation is the sort of radiation we associate with radioactive substances like uranium, radium, and the fall-out from atomic and thermonuclear explosions. Non-ionizing radiation is very different. Because of the lower frequencies and reduced energy, it does not have the same damaging and cumulative properties as ionizing radiation.

Microwave radiation (at 2450 MHz) is non-ionizing, and in sufficient intensity will simply cause the molecules in certain types of matter to vibrate, thereby causing friction, which produces the heat that cooks the food. 

Now that we know what is on either side of microwaves in the EM spectrum - radio waves on one side and radar and television waves on the other, we know that there is non-ionizing EM waves surrounding the microwave. So...what is the scare all about???

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