Let There Be Light
As Hertz proved, light is an electromagnetic wave. And all such waves, whether they are x-rays, ultra-violet, micro-waves, infra-red, radio or TV waves, or visible light, have the same basic properties.
And fascinating properties they are. In any EM wave there are 3 directions of motion, and all three are at right angles to each other. What a cool concept, eh? What are the 3 directions? Well, the most obvious is the direction that the wave is traveling, like from the Radio Station to your antenna. But in each wave there is an electric force field and a magnetic force field. Thus the name electromagnetic. The electric force field moves up and down at right angles to the direction of travel of the wave. And the magnet field moves up and down at right angles to the electric field, and to the direction of travel. It is easier to grasp with a diagram:
Or here is a Flash Animation showing the motion of an EM wave:
transverse-electromagnetic-wave
Other than its basic structure the other extremely interesting thing about EM waves is the duality of its nature. A change in electric force (keyword change) will produce a magnetic field. Conversely, a change in magnetic field will produce an electric field. In other words the constant flow of electricity like in a battery won't do anything, but and increase or decrease in electric force creates a corresponding magnetic field. Likewise an increase or decrease (not just a constant force) in a magnetic field will make an electric force.
So this creates an interesting chain effect. How do you kill an EM Wave. When an electric field collapses, this action causes a magnetic field to curl around it. The very collapse of the field is a change. When the magnetic field collapses, it creates (re-incarnates?) an electric field. And so on, forever, in perpetual motion. Once started this action continues on without end. You can blow out the candle but not the light it creates.
One more interesting thing about EM Waves. As you may have noticed, there is no way to picture an EM Wave in less than 3 dimensions. This is relatively unique in physics. You can picture a sound wave, for example, in 1 or 2 dimensions. In fact all of the laws of mechanical physics can be represented in the 2 dimensions of the surface of a pool table. But not so with light and EM Waves. Hey, who made these rules up, anyway?
And fascinating properties they are. In any EM wave there are 3 directions of motion, and all three are at right angles to each other. What a cool concept, eh? What are the 3 directions? Well, the most obvious is the direction that the wave is traveling, like from the Radio Station to your antenna. But in each wave there is an electric force field and a magnetic force field. Thus the name electromagnetic. The electric force field moves up and down at right angles to the direction of travel of the wave. And the magnet field moves up and down at right angles to the electric field, and to the direction of travel. It is easier to grasp with a diagram:
Or here is a Flash Animation showing the motion of an EM wave:
transverse-electromagnetic-wave
Other than its basic structure the other extremely interesting thing about EM waves is the duality of its nature. A change in electric force (keyword change) will produce a magnetic field. Conversely, a change in magnetic field will produce an electric field. In other words the constant flow of electricity like in a battery won't do anything, but and increase or decrease in electric force creates a corresponding magnetic field. Likewise an increase or decrease (not just a constant force) in a magnetic field will make an electric force.
So this creates an interesting chain effect. How do you kill an EM Wave. When an electric field collapses, this action causes a magnetic field to curl around it. The very collapse of the field is a change. When the magnetic field collapses, it creates (re-incarnates?) an electric field. And so on, forever, in perpetual motion. Once started this action continues on without end. You can blow out the candle but not the light it creates.
One more interesting thing about EM Waves. As you may have noticed, there is no way to picture an EM Wave in less than 3 dimensions. This is relatively unique in physics. You can picture a sound wave, for example, in 1 or 2 dimensions. In fact all of the laws of mechanical physics can be represented in the 2 dimensions of the surface of a pool table. But not so with light and EM Waves. Hey, who made these rules up, anyway?
posted by Eclectricz at
9:02 PM
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