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I'm sorry to disappoint you but I don't know what electromagnetic waves are. But then nobody else does either. I can't tell you exactly what travels through space to your radio so it can play music, or to your television so it can show a picture, or what makes x-rays display an image on photographic film. I also don't know what magnetism is, or gravity is either. Nobody knows. These many of the things we all just accept that defy direct observation. But that doesn't mean they're a total mystery. It turns out that by doing clever investigation coupled with some amazing discoveries we can get a pretty good handle on a lot of things we can't observe directly. A good example of this is the atom. Never seen one, and it's unlikely we ever will. But we know a lot about them and we have put that acquired knowledge to work in some marvelous ways. Same can be said for electromagnetic waves, which from now on we'll just call EM waves. By the way, don't let the graphic above intimidate you. It will all become clear in just a moment. If we are going to understand waves we have to identify and define them. This is the first step to nailing these suckers down and getting them to confess what they are. So here we go. In the english language the word wave is used to describe a number of things. From the hand gesture across a room, to the flag that is fluttering in the wind or the water that comes crashing up on to the beach. It can be used to describe sound too. As you know from our previous discussions sound vibrations are mechanical in nature and require a medium to travel in, such as air or a solid material. Sound vibrations travel in waves and the higher or faster the they are, the higher the pitch. The slower they are the lower the pitch. Sound is similar to EM waves because they also vibrate, but that is where the similarity ends. EM waves don't require a material to travel in and they aren't generated by a mechanical process such as a speaker or vocal cords. Now its time to examine the graphic above. It seems that EM waves occur naturally. There all around us and are a common part of the big picture. They can come from the sun, from outer space or we can make them. They can be pretty lazy and large ones like the low frequency hum of a transformer or they can be very active and small like gamma rays. (Frequency is a word to used to indicate how fast a wave moves from a high peak to a low peak and how often and it comes from the root word frequent.) In the graphic above we are going to define our understanding of a wave. Across the top is a representation of the waves that travel through the air (or in a vacuum because the waves permeate everything to some degree. You will notice that the visible light waves that our eyes can see occupies a very limit range on the frequency scale. The other numbers are just as real but we aren't able to see them, but they are made up of the same thing. It might seem obvious but we are capable of making these frequencies and you surely recognize these. The most common are the microwaves, infrared, ultraviolet and x-rays. Radio waves and Television are in the same scale. To better understand what a wave is look at the representation in the lower left. It shows how a cycle of continuous waves travels through time. And it is time that makes it all real and time is another one of those mysteries we don't truly understand. Look in the lower right at the blue circles. This represents the ripples in a pond but it is another way to show how a wave works. Strange as it might seem if you could increase the ripples to the point where they moved at a high enough speed light they could be turned into visible light. This sort of tells use that everything exists because of motion, even down to the sub atomic level. Click on the picture. Here is a graphic showing a short section of the wave geography. In this one we see the area where radio and television resides. We can't see them but we know they are there from indirect observation and also because we use them everyday. From cell phones to cosmic rays we are awash in waves from everywhere.
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