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fckm · 11-30-2004, 07:55 PM

Light is not movement. Nothing is moving.
(this gets hard to describe)

The Electric Field (and the mag. field for that matter) are Force Fields. So, a force is a vector that points in a direction and has a magnitude. The magnitude of the force tells us how much the momentum is changing, and the direction tells us in what direction it's changing.

A field, is a mathematical concept, where every single point in space is assigned some value. For example, think of Temperature. Every single point in your room has some temperature. The temperature can vary. The temperature by your computer is probably larger than the temperature at your window. This is called a scalar field.

Now, let's think about wind. You go outside on a summer day, and it's windy out. But its not windy everywhere, some places are more windy than others. The wind is a vector field. A every point in space, the wind has a direction (the direction can be different depending on where you are) and a certain magnitude (the windyness can be different depending on where you are).

The E-field is a vector Force Field. By itself, the E-field doesn't do much. But, if you take an electron and hold it in your hand, and move it around in the E-field, you can feel a force on the electron. The force will vary in direction and magnitude depending on where that electron is. Now imagine that the E-field changes in time too. So if you hold your electron at a certain point in space, you will feel the force on that electron change in time. At one instant, the electron is pushed to the left. A second later, the electron is pushed to the right.

Now, let's take away the electron. Even though the electron is gone, the FIELD is still there. This is where our analogy to wind breaks down. Take away the air, and there's no more wind.

Light, is "waves" in the E-Field. Think of a wave on a string. Think of one point on that string. A one moment, that point is very high. A second later, that point is now in the rest postion of the string. In the next moment, the point is really low.

Transfer this over to the E-Field. Take our test charge and put it at a point. At one moment, the test charge feels a force to the left. As time progresses, the pull of that force decrease, untill it stops feeling a force at all. Then, there is a small force to the right, and the pull of that force increase with time, and starts decreasing again. This is an oscilation in the E-Field. Now imagine this happening at every point in space. Only, each point is slightly "out of synch" with it's neighbor. This is a wave in the E-field.

Now, lets take that electron away again. Even though the electron isn't there, the E-field still exists and that oscillation in the E-field still exists. This is light. Light is not a movement of anything, it is a change in the Electric Force Field. This change has certain characteristics in space and time.

How do we see/measure light? Well, our eyeballs are made of atoms, and atoms have charged particles. When that "wave" hits our eyeball, it gives atoms and electrons energy, which causes chemical reactions, which causes nerve impluses, etc.

How do we make light? Light is oscillations of the EM field. Where do EM fields come from? They come from charged particles (protons and electrons, etc). Each charged particle gives off a constant field. If we wiggle the particles, we can imagine that this wiggle propogates throughout space. This wiggle is the oscillation of the field. Thus, wiggling/accelerating charged particles creates light.

11-30-2004, 07:55 PM	#29 (permalink)
fckm Insane Location: Ithaca, New York	Light is not movement. Nothing is moving. (this gets hard to describe) The Electric Field (and the mag. field for that matter) are Force Fields. So, a force is a vector that points in a direction and has a magnitude. The magnitude of the force tells us how much the momentum is changing, and the direction tells us in what direction it's changing. A field, is a mathematical concept, where every single point in space is assigned some value. For example, think of Temperature. Every single point in your room has some temperature. The temperature can vary. The temperature by your computer is probably larger than the temperature at your window. This is called a scalar field. Now, let's think about wind. You go outside on a summer day, and it's windy out. But its not windy everywhere, some places are more windy than others. The wind is a vector field. A every point in space, the wind has a direction (the direction can be different depending on where you are) and a certain magnitude (the windyness can be different depending on where you are). The E-field is a vector Force Field. By itself, the E-field doesn't do much. But, if you take an electron and hold it in your hand, and move it around in the E-field, you can feel a force on the electron. The force will vary in direction and magnitude depending on where that electron is. Now imagine that the E-field changes in time too. So if you hold your electron at a certain point in space, you will feel the force on that electron change in time. At one instant, the electron is pushed to the left. A second later, the electron is pushed to the right. Now, let's take away the electron. Even though the electron is gone, the FIELD is still there. This is where our analogy to wind breaks down. Take away the air, and there's no more wind. Light, is "waves" in the E-Field. Think of a wave on a string. Think of one point on that string. A one moment, that point is very high. A second later, that point is now in the rest postion of the string. In the next moment, the point is really low. Transfer this over to the E-Field. Take our test charge and put it at a point. At one moment, the test charge feels a force to the left. As time progresses, the pull of that force decrease, untill it stops feeling a force at all. Then, there is a small force to the right, and the pull of that force increase with time, and starts decreasing again. This is an oscilation in the E-Field. Now imagine this happening at every point in space. Only, each point is slightly "out of synch" with it's neighbor. This is a wave in the E-field. Now, lets take that electron away again. Even though the electron isn't there, the E-field still exists and that oscillation in the E-field still exists. This is light. Light is not a movement of anything, it is a change in the Electric Force Field. This change has certain characteristics in space and time. How do we see/measure light? Well, our eyeballs are made of atoms, and atoms have charged particles. When that "wave" hits our eyeball, it gives atoms and electrons energy, which causes chemical reactions, which causes nerve impluses, etc. How do we make light? Light is oscillations of the EM field. Where do EM fields come from? They come from charged particles (protons and electrons, etc). Each charged particle gives off a constant field. If we wiggle the particles, we can imagine that this wiggle propogates throughout space. This wiggle is the oscillation of the field. Thus, wiggling/accelerating charged particles creates light. __________________ And if you say to me tomorrow, oh what fun it all would be. Then what's to stop us, pretty baby. But What Is And What Should Never Be.