light waves?

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

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

Quote:

Originally posted by lyghtningbyrd
So, if light travels in a straight line.....

More correctly, light follows the curvature of space.

Quote:

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?

Quote:

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

LuxFerum · 13th October 2003, 07:06 AM

and to the other side

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

Quote:

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

Quote:

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

Quote:

Originally posted by Ziggurat
Hope that helps.

It sure does. Very well explained. My confusion has diappeared now. Thanks.

13th October 2003, 12:05 AM	#1
lyghtningbyrd Scholar Join Date: Apr 2003 Posts: 114	light waves? 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.
lyghtningbyrd Scholar Join Date: Apr 2003 Posts: 114	__________________ Support your local Apathy Club.

13th October 2003, 12:46 AM	#2
a_unique_person Director of Hatcheries and Conditioning Join Date: Jul 2002 Location: Mt Disappointment Posts: 33,341	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.
	__________________ *Continually pushing the boundaries of mediocrity.* Everything is possible, but not everything is probable. For if a man pretend to me that God hath spoken to him supernaturally, and immediately, and I make doubt of it, I cannot easily perceive what argument he can produce to oblige me to believe it. Hobbes

13th October 2003, 01:41 AM	#3
LuxFerum Augustus Join Date: Dec 2002 Location: Brazil Posts: 5,417	Light moves like this But light is not going up and down, it moves strait forward. That is just the representation of his electromagnetic fields.
	__________________ Jos kad bih znala sta pametno da napisem! Eh, nikad se ne zna. Mozda me netko i razumije. - Tanja Age and treachery will always overcome youth and skill. Well, if crime fighters fight crime and fire fighters fight fire, what do freedom fighters fight? They never mention that part to us, do they? - George Carlin

13th October 2003, 05:21 AM	#4
BillyJoe Penultimate Amazing Join Date: Aug 2001 Location: MOOROOLBARK Posts: 12,539	Luxy, the left side of that picture is confusing. The waves should just extend out to the left edge of the frame.
	__________________ A secular society is one in which no one loses any liberty as a consequence of someone else's religious beliefs. NB Allowing yourself to get led around the nose by a person like Craig is a losing strategy. SH Morality is a social coating around a Darwinian core. JC My joke about freewill: There is no basis for it.

13th October 2003, 05:34 AM	#5
BillyJoe Penultimate Amazing Join Date: Aug 2001 Location: MOOROOLBARK Posts: 12,539	Re: light waves? Quote: Originally posted by lyghtningbyrd So, if light travels in a straight line..... More correctly, light follows the curvature of space. Quote: 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? Quote: 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)
	__________________ A secular society is one in which no one loses any liberty as a consequence of someone else's religious beliefs. NB Allowing yourself to get led around the nose by a person like Craig is a losing strategy. SH Morality is a social coating around a Darwinian core. JC My joke about freewill: There is no basis for it.

13th October 2003, 06:09 AM	#6
pupdog Muse Join Date: Dec 2002 Location: Pennsylvania Posts: 627	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?
	__________________ Professor Pupdog

13th October 2003, 07:01 AM	#7
LuxFerum Augustus Join Date: Dec 2002 Location: Brazil Posts: 5,417	here it is
	__________________ Jos kad bih znala sta pametno da napisem! Eh, nikad se ne zna. Mozda me netko i razumije. - Tanja Age and treachery will always overcome youth and skill. Well, if crime fighters fight crime and fire fighters fight fire, what do freedom fighters fight? They never mention that part to us, do they? - George Carlin

13th October 2003, 07:06 AM	#8
LuxFerum Augustus Join Date: Dec 2002 Location: Brazil Posts: 5,417	and to the other side from here http://www.enzim.hu/~szia/cddemo/edemo0.htm
	__________________ Jos kad bih znala sta pametno da napisem! Eh, nikad se ne zna. Mozda me netko i razumije. - Tanja Age and treachery will always overcome youth and skill. Well, if crime fighters fight crime and fire fighters fight fire, what do freedom fighters fight? They never mention that part to us, do they? - George Carlin

13th October 2003, 08:32 AM	#9
espritch Graduate Poster Join Date: Jul 2002 Posts: 1,380	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).
	__________________ "I'm the master of low expectations." - G. W. Bush

13th October 2003, 10:21 AM	#10
Ziggurat Penultimate Amazing Join Date: Jun 2003 Posts: 26,224	Quote: 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.
	__________________ "As long as it is admitted that the law may be diverted from its true purpose -- that it may violate property instead of protecting it -- then everyone will want to participate in making the law, either to protect himself against plunder or to use it for plunder. Political questions will always be prejudicial, dominant, and all-absorbing. There will be fighting at the door of the Legislative Palace, and the struggle within will be no less furious." - Bastiat, The Law

13th October 2003, 01:54 PM	#11
Jethro Thinker Join Date: Apr 2002 Posts: 142	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.
Jethro Thinker Join Date: Apr 2002 Posts: 142

13th October 2003, 02:24 PM	#12
plindboe Graduate Poster Join Date: Apr 2003 Location: Denmark Posts: 1,244	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.
	__________________ Peter "The whole problem with the world is that fools and fanatics are always so certain of themselves, but wiser people so full of doubts." (Bertrand Russell)

13th October 2003, 02:36 PM	#13
Ziggurat Penultimate Amazing Join Date: Jun 2003 Posts: 26,224	Quote: 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.
	__________________ "As long as it is admitted that the law may be diverted from its true purpose -- that it may violate property instead of protecting it -- then everyone will want to participate in making the law, either to protect himself against plunder or to use it for plunder. Political questions will always be prejudicial, dominant, and all-absorbing. There will be fighting at the door of the Legislative Palace, and the struggle within will be no less furious." - Bastiat, The Law

13th October 2003, 03:45 PM	#14
plindboe Graduate Poster Join Date: Apr 2003 Location: Denmark Posts: 1,244	Quote: Originally posted by Ziggurat Hope that helps. It sure does. Very well explained. My confusion has diappeared now. Thanks.
	__________________ Peter "The whole problem with the world is that fools and fanatics are always so certain of themselves, but wiser people so full of doubts." (Bertrand Russell)