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lyghtningbyrd
13th October 2003, 12:05 AM
First of all, I am not a scientist or mathematician. I need help understanding a slightly abstract and bizarre concept. I am under the impression that current scientific thought on light suggests that it is both particles and wave. If this is correct, I need help understanding the wave part.

If a wave travels like this:~~~~~
it would look like this stretched out:--------------

So, if light travels in a straight line, how does the light wave go a further distance that the light itself? Is it going faster than the speed of light? Does that even make sense?

Perhaps I have some misconceptions about what a wave is, be it light, radio, or otherwise.

If anyone can find a way to rationalize and explain this to me in laymens terms, please do. Thanks.

a_unique_person
13th October 2003, 12:46 AM
litning, we have are pesky troll around at the moment. If you do not get an answer, it may because people are wary that you are it.

LuxFerum
13th October 2003, 01:41 AM
Light moves like this
http://www.enzim.hu/~szia/cddemo/p3.gif
But light is not going up and down, it moves strait forward.
That is just the representation of his electromagnetic fields.

BillyJoe
13th October 2003, 05:21 AM
Luxy, the left side of that picture is confusing. The waves should just extend out to the left edge of the frame.

BillyJoe
13th October 2003, 05:34 AM
Originally posted by lyghtningbyrd
So, if light travels in a straight line.....More correctly, light follows the curvature of space.

Originally posted by lyghtningbyrd
....how does the light wave go a further distance that the light itself? If we consider light to be a wave, how can the wave which constitutes the light travel faster than light?

Originally posted by lyghtningbyrd
Is it going faster than the speed of light? Does that even make sense? As you guessed, no, it doesn't.

Of course, the wave and particle models of light ARE just models. They are merely means to an end, which is to help us to make predictions about the world. What light actually is, is probably not a question we will ever be able to answer. But we can always improve on our models so as to make better predictions.

So, no, our model of light does not travel faster than light otherwise it would not be a very good model.

BillyJoe
(Of course, physicists feel free to correct any of the above)

pupdog
13th October 2003, 06:09 AM
Light (electromagnetic) waves differ from mechanical waves such as you see on a body of water. In water waves, particles (of water) move up and down but the wave (seen as crests and troughs) moves along the surface of the water. With light, the electromagnetic intensities move up and down (vary perpendicular to the ray, or direction of wave travel, as the wave moves.

K-12 science had lots of gadgets showing wave propagation (but no net movement of particles). There wasn't anything to show photon travel.

Can LuxFerum provide an animation explaining circular polarization?

LuxFerum
13th October 2003, 07:01 AM
here it is :D

http://www.enzim.hu/~szia/cddemo/p4.gif

LuxFerum
13th October 2003, 07:06 AM
and to the other side :D

http://www.enzim.hu/~szia/cddemo/p5.gif

from here
http://www.enzim.hu/~szia/cddemo/edemo0.htm

espritch
13th October 2003, 08:32 AM
Some one correct me if I'm wrong, but I seem to recall that the light wave has two components at right angles to one another: the electric component and the magnetic component. These are offset so that the electric component increases as the magnetic component decreases and vise versa. Lux's illustration shows both components in sync, which is, I think, not quite correct.

Light is viewed as a wave because it exhibits wave like properties such as interference. It is viewed as a particle because it transports energy in discreet amounts (the energy of a single photon). Of course both views are attempts to explain the behaviour of something that we can not directly observe (we can only observe the interaction of the photon - or light wave - with something else).

Ziggurat
13th October 2003, 10:21 AM
Originally posted by espritch
Some one correct me if I'm wrong, but I seem to recall that the light wave has two components at right angles to one another: the electric component and the magnetic component. These are offset so that the electric component increases as the magnetic component decreases and vise versa. Lux's illustration shows both components in sync, which is, I think, not quite correct.

You are correct. However, the two components being shown are both electric (or both magnetic). What's being shown is how component polarizations add up. If the components add in phase, it's linearly polarized in some intermediate direction (the first figure). If they add up out of phase, the light is circularly polarized (the last two). But the EM field equations are linear, so classically you can treat the components (vertical polarization and horizontal polarization) separately.

Jethro
13th October 2003, 01:54 PM
Light is a wave, but this does not mean that the light particles are traveling up and down along the path of the light ray. Everyone else here has explained what it does mean.

plindboe
13th October 2003, 02:24 PM
I'm quite tired, which is probably the reason why I don't get it. I'm wondering in that model, for instance what the blue line is. It travels overall a longer path, per time, than the white line that moves straight does, so it travels faster than the light itself. Please explain it like you are talking with Rain Man, or my tired mind won't be able to understand,:( thanks.

Ziggurat
13th October 2003, 02:36 PM
Originally posted by plindboe
I'm quite tired, which is probably the reason why I don't get it. I'm wondering in that model, for instance what the blue line is. It travels overall a longer path, per time, than the white line that moves straight does, so it travels faster than the light itself. Please explain it like you are talking with Rain Man, or my tired mind won't be able to understand,:( thanks.

Well, the confusing part is only one of the axes is a spatial axis (the white line). The other two axes represent the magnitude of the electric (or magnetic) field along a spatial axis. In other words, given a STRAIGHT line of travel for the photon, the electric field points sideways from that line, but it's still the field ON that line that we're interested in. It's being represented by the blue line, but it's really a vector ON the white line pointing in the direction of the blue line, with a magnitude equal to the distance of the blue line from the white line. So it's just a way of representing the fact that the field at a single point still has both a direction and a magnitude. But nothing is actually moving along any curved path, the wave still travels in a straight line. Hope that helps.

plindboe
13th October 2003, 03:45 PM
Originally posted by Ziggurat
Hope that helps.
It sure does. Very well explained. My confusion has diappeared now. Thanks.