Can light be deflected in an electric field

[touqra]

Can light be deflected in an electric field, since light wave has an electric component and a magnetic component?

 

[fargoth]

light is the moving change of electro-magnetic field in space, constant electric field won't change its behaviour.

its like rising the water level and expecting the waves on the surface to deflect.

but changing the viscosity of the liquid at a certain interval will deflect the wave on the surface, just like changing the dialectric value in which the light travels (or magnetic permeability) deflects light.

 

[Doc Al]

Can light be deflected in an electric field, since light wave has an electric component and a magnetic component?

No. Electric fields would deflect the path of a charged particle, but not light, which carries no charge. (At extremely high intensities, there can be photon-photon interactions that do affect the path of the light, but I believe that the most direct answer to your question is still "no" for all practical purposes.)

 

[EL]

Can light be deflected in an electric field, since light wave has an electric component and a magnetic component?

According to the classical theory, that is Maxwell's equations, electromagnetic fields cannot interact with each other in vacuum. This follows directly from the fact that Maxwell´s equations in vacuum are linear in the electromagnetic fields.

However, if we as Doc Al said, consider extremely intense fields, the classical theory does not hold anymore, but we have to use the quantum theory of electrodynamics, that is QED (Quantum ElectroDynamics).
QED is a non-linear theory, and infact allows for this type of interactions thanks to so called virtual particles, although the cross-section for the interaction is very tiny. But the process you are asking about, so called Delbrück scattering, has indeed quite recently been detected in laboratory.

I may add that another related process, photon-photon scattering, where light is scattered by light, has not yet been detected, but thanks to advances in high power laser technology, this will probably happen within a near future.

 

[abszero]

photon-photon scattering as I understand is a fourth order effect, where you have two pair productions, the pairs interact then annihilate, and the emitted photons appear to be scattered from the original two. Is this correct?

 

[EL]

photon-photon scattering as I understand is a fourth order effect, where you have two pair productions, the pairs interact then annihilate, and the emitted photons appear to be scattered from the original two. Is this correct?

Well, not exactly, but almost.
The lowest order Feynman diagram for photon-photon scattering has four vertices and consists of two incoming photons, which annihilate into a virtual electron-positron pair, which then annihilates into two real photons again. However, note that the intermediate electron-positron pair is just virtual, so the incoming photons need not be energetic enough for real pair creation.
So photon-photon scattering does not really happen through "two step", it's just that the lowest order Feynman diagram looks like that.

 

[touqra]

No. Electric fields would deflect the path of a charged particle, but not light, which carries no charge. (At extremely high intensities, there can be photon-photon interactions that do affect the path of the light, but I believe that the most direct answer to your question is still "no" for all practical purposes.)

How then would we prove that there is an electric component in light?

 

[pinestone]

If light waves pass in close proximity to our Sun, they "bend" slightly from the Sun's gravitational influence. Isn't gravity considered to be an electromagnetic phenomenon?

 

[Claude Bile]

How then would we prove that there is an electric component in light?

The fact that the observed speed of light precisely matches the calculated speed of an electromagentic wave is fairly solid evidence. In fact, all the (classical) observed properties of light are predicted by classical EM theory.

Claude.

 

[Bob3141592]

If light waves pass in close proximity to our Sun, they "bend" slightly from the Sun's gravitational influence. Isn't gravity considered to be an electromagnetic phenomenon?

No, gravity is quite distinct. Whether it's framed as gravitons or as curvature of space-time, there's no electromagnetic components to it.

 

[ZapperZ]

How then would we prove that there is an electric component in light?

You use the E-field component to accelerate charged particles. And VOILA! That's what we do in particle accelerators! RF cavities and LINAC use electromagnetic fields (I use standing wave cavity in TM mode) where by the E-field component of the EM field is the accelerating field.

Zz.

 

[Meir Achuz]

If light waves pass in close proximity to our Sun, they "bend" slightly from the Sun's gravitational influence. Isn't gravity considered to be an electromagnetic phenomenon?

EM waves have an energy density.
Gravitation acts on any kind energy. There is nothing EM about gravity.

 

[pinestone]

How does gravity bend light?

 

[Tide]

How does gravity bend light?

Technically, it doesn't. Photons travel along geodesics (i.e. the shortest path from A to B like great circles on a globe) but the space through which they travel in the presence of a gravitating mass is curved and so to a distant observer the path of a photon appears to curve.

 

[pinestone]

...and so to a distant observer the path of a photon appears to curve.

In reality, observation is light. If it appears to bend, then it does bend. A strong magnetic field can also bend light- correct?

 

[ZapperZ]

In reality, observation is light. If it appears to bend, then it does bend. A strong magnetic field can also bend light- correct?

No, this is not the same thing. When you see something bends, you are seeing it bends IN SPACE, i.e. the FRAME that you are using to look at it does NOT alter. Try drawing a curved line on a cartesian grid. The grid doesn't curve. So you can see, based on the straight lines, that there is a bend in the curve.

But a bend in space-time is where the "grid" itself is distorted. Your "frame" is the thing that is being bent. Even the use of the word "bend" isn't quite right becuase this is a rather naive view of a complex mathematical situation. If you're tracing the path of light in this frame, you do not notice where it "curves". You only detect that it has gone around an object only via a later detection.

Be very careful in translating a mathematical description into "words". Never put more emphasis on the words than the mathematical formulation.

Zz.

 

[pinestone]

...Be very careful in translating a mathematical description into "words". Never put more emphasis on the words than the mathematical formulation.
Zz.

"As far as the laws of mathematics refer to reality, they are not certain, as far as they are certain, they do not refer to reality."- Albert Einstein.
Light can be bent, ie. its polarization can be altered by a magnetic field.

 

[Meir Achuz]

A static magnetic field does not bend light. A rapidly oscillating field could.
It would be a QFT effect that would not occur classically.

 

[ZapperZ]

"As far as the laws of mathematics refer to reality, they are not certain, as far as they are certain, they do not refer to reality."- Albert Einstein.

Before you think you can play "quote the scientist" with me, let me put a stop to that and tell you that I'm not impressed. I will challenge you if you even KNOW what exactly is meant by that quote. It is highly annoying when I put EFFORT into explaining the PHYSICS of what is going on, and all you can rebutt is a quote that you don't even understand!

If all you can do, and if all you think physics is, is just a bunch of quotations taken out of context, then you have zero idea how physics is practiced.

Light can be bent, ie. its polarization can be altered by a magnetic field.

Show me EXACTLY where (i) theoretically this has been shown and (ii) experimentally this has been verified. And just in case you think you can simply show a quack website as a legitimate source, let me diffused that right now.

Zz.

 

[Tide]

A strong magnetic field can also bend light- correct?

I don't think so.

Regarding light and gravity, read what Zapper said - carefully! He spelled it out very well. :)

 

[pinestone]

Before you think you can play "quote the scientist" with me, let me put a stop to that and tell you that I'm not impressed. I will challenge you if you even KNOW what exactly is meant by that quote. It is highly annoying when I put EFFORT into explaining the PHYSICS of what is going on, and all you can rebutt is a quote that you don't even understand!
If all you can do, and if all you think physics is, is just a bunch of quotations taken out of context, then you have zero idea how physics is practiced.
Show me EXACTLY where (i) theoretically this has been shown and (ii) experimentally this has been verified. And just in case you think you can simply show a quack website as a legitimate source, let me diffused that right now.
Zz.

First, let me say "thank you" for spending your precious time and efforts helping others understand physics. Many only think about themselves, and no one else. Second, I'm not trying to "piss" anyone off with my statements. As, I'm trying to understand these mysteries, too. I may not have the formal education that you do, but 30+ years of experimental physics have made many realities obvious to me. Third and finally, See: http://www.teachspin.com/instruments/faraday/index.shtml
If you think that is a "quack" website, find a good book on Faraday.

 

[ZapperZ]

First, let me say "thank you" for spending your precious time and efforts helping others understand physics. Many only think about themselves, and no one else. Second, I'm not trying to "piss" anyone off with my statements. As, I'm trying to understand these mysteries, too. I may not have the formal education that you do, but 30+ years of experimental physics have made many realities obvious to me. Third and finally, See: http://www.phy.hr/~dpaar/fizicari/xfaraday.html
If you think that is a "quack" website, find a good book on Faraday.

Are you completely unaware that electromagnetism has progressed SIGNIFICANTLY since Faraday? Do you think Faraday saw Special Relativity, General Relativity, Quantum Mechanics, Quantum Electrodynamics, etc? I'm shocked you are not here trying to sell the Caloric theory of heat!

And no, you are NOT ".. trying to understand.." anything. You MADE STATEMENTS about properties of light! When I explained why your statements were wrong, how did you counter that? With a QUOTE and an outdated physics pointing to Faraday.

Get this very clear - Faraday made tons of contributions to electromagnetic theory - and all of them can be found in any classical E&M text. Now since, by citing Faraday, you BUY his discoveries, show me where in classical E&M is light affected by magnetic field. Go on, take a look at Maxwell equations and show me where there exists a description of light being bent by either E of B field.

You pay way too much attention to sites and quotes without understanding the exact formulations. You seem to not care that there is a distinct difference between a superficial knowledge of the stuff you read, and having a really good understanding of it. I can't possibly believe that even you would think that reading websites like the one you cited is sufficient to tackle the phenomenon of light and E&M. Yet, you have to hesitation in arguing based on those superficial knowledge.

Open an E&M text. All the websites you can cite cannot even amount to a hill of beans when compared to Griffith's text, for example. Until you make an effort at understanding the formulation, you are basing your arguments and understanding on superficial understanding of a popular science text. Nothing productive has come out of such a discussion.

Zz.

 

[pinestone]

...Are you completely unaware that electromagnetism has progressed SIGNIFICANTLY since Faraday? Zz.

So are you saying that Faraday was wrong and that the polarization of light won't be rotated by a strong magnetic field? I thought this forum was "classical physics"- QED is not very classical.

 

[ZapperZ]

So are you saying that Faraday was wrong and that the polarization of light won't be rotated by a strong magnetic field?

Show me the physics that Faraday is describing. And then show me the EXPERIMENTAL VERIFICATION of such an effect.

Zz.

 

[pinestone]

Show me the physics that Faraday is describing. And then show me the EXPERIMENTAL VERIFICATION of such an effect.
Zz.

The effect, manifested as an induced optical activity, is able to rotate the plane of polarisation of an input optical beam which propagates parallel to the direction of the magnetic field in the material. The strength of the effect is simply given by the formula:
theta=BVl
where theta is the angle of rotation; B is the magnetic field in tesla, V is the Verdet constant for the material and l is the effective length of material contained within the magnetic field. Here's more if you care to look:http://farside.ph.utexas.edu/teaching/jk1/lectures/node60.html
Buy a Faraday rotation device here: http://www.teachspin.com/instruments/faraday/index.shtml
You didn't answer my question. Was Faraday wrong?

 

[ZapperZ]

The effect, manifested as an induced optical activity, is able to rotate the plane of polarisation of an input optical beam which propagates parallel to the direction of the magnetic field in the material. The strength of the effect is simply given by the formula:
theta=BVl
where theta is the angle of rotation; B is the magnetic field in tesla, V is the Verdet constant for the material and l is the effective length of material contained within the magnetic field. Here's more if you care to look:http://farside.ph.utexas.edu/teaching/jk1/lectures/node60.html
Buy a Faraday rotation device here: http://www.teachspin.com/instruments/faraday/index.shtml
You didn't answer my question. Was Faraday wrong?

Just as I thought!

Would you please READ ALL of your posts. Nowhere in those were there EVER a mention of a "medium" in which light is passing through! At every step of the way, we were discussing about a motion of light in vacuum. This is what the OP asked!

But please re-read the site YOU have given me. What in the world did you think a "dielectric medium" is? When light passes though a medium/solid such as that, all bets are off! I can make it turn into a circularly polarized light if I want to. Hell, I can even make it move at 0 m/s! Just ask Lena Hau!

Again, PAY ATTENTION to the details! A magnetic field does not affect light. A magnetic field (and electric field) can affect the medium that induces a number of factors that can change the optical transmission of light. I should know - I studied such things. Optical transmission in solids is NOT the same as its transmission in vacuum.

This is another illustration on WHY I asked you for the PHYSICS rather than hand-waving argument. As soon as you pointed out to this, I KNEW my guess was right.

Zz.

 

[pinestone]

Just as I thought!
Would you please READ ALL of your posts. Nowhere in those were there EVER a mention of a "medium" in which light is passing through! At every step of the way, we were discussing about a motion of light in vacuum. This is what the OP asked!
But please re-read the site YOU have given me. What in the world did you think a "dielectric medium" is? When light passes though a medium/solid such as that, all bets are off! I can make it turn into a circularly polarized light if I want to. Hell, I can even make it move at 0 m/s! Just ask Lena Hau!
Again, PAY ATTENTION to the details! A magnetic field does not affect light. A magnetic field (and electric field) can affect the medium that induces a number of factors that can change the optical transmission of light. I should know - I studied such things. Optical transmission in solids is NOT the same as its transmission in vacuum.
This is another illustration on WHY I asked you for the PHYSICS rather than hand-waving argument. As soon as you pointed out to this, I KNEW my guess was right.
Zz.

Ok, I'll try and be more detailed with my statements. I'm not trying to be difficult or create "waves". I appreciate your continued efforts to reveal the truth with words, instead of mathematics. So, your answer is NO. Light traveling through a vacuum can not be deflected by a magnetic field. My answer is YES. Light traveling through a dielectric can be deflected by a magnetic field.

 

[ZapperZ]

Ok, I'll try and be more detailed with my statements. I'm not trying to be difficult or create "waves". I appreciate your continued efforts to reveal the truth with words, instead of mathematics. So, your answer is NO. Light traveling through a vacuum can not be deflected by a magnetic field. My answer is YES. Light traveling through a dielectric can be deflected by a magnetic field.

And I can show you where using a different dielectric medium where this will NOT occur. Why? Because it depends ON THE MATERIAL! Try it! I'll suggest one: a photonic band gap material! Use light with energy LESS than the size of the photonic band gap. Apply as much magnetic field as you want. You'll NEVER get the light to be "deflected".

Learn condensed matter physics, especially optical transmission in solids, before you proclaim such a thing.

Zz.

 

[EL]

A magnetic field does not affect light.

According to classical electrodynamics you are right.
According to QED you are wrong.
"According to reality" I think you are wrong, but actually I'm not sure if light scattering by a magnetic field has ever been observed. However, what I'm sure of is that light scattering by an electric field from a nucleus, that is Delbrück scattering, has been observed. And that's why I have no doubts in that light can be scattered by a magnetic field too.

 

[EL]

A static magnetic field does not bend light. A rapidly oscillating field could.
It would be a QFT effect that would not occur classically.

Why wouldn't a static magnetic field work?
We have detected it for a static electric field, so I don't see what would be the difference?
(Ok, actually I think "scattering" is a better word than "bending".)

 

[ZapperZ]

According to classical electrodynamics you are right.
According to QED you are wrong.
"According to reality" I think you are wrong, but actually I'm not sure if light scattering by a magnetic field has ever been observed. However, what I'm sure of is that light scattering by an electric field from a nucleus, that is Delbrück scattering, has been observed. And that's why I have no doubts in that light can be scattered by a magnetic field too.

But you'll notice that we're not even up to THAT level here. QED predicts this as a higher order interactions. QED also predicts photon-photon scattering. Both of these have NOT been observed and verified experimentally.

Moreoever, if you have followed this thread, we are STUCK in classical E&M and haven't made any progress in establishing even THAT! I certainly am not in the mood to bring in QED when it is not clear that the parties in question don't even know classical E&M.

Zz.

 

[EL]

But you'll notice that we're not even up to THAT level here. QED predicts this as a higher order interactions. QED also predicts photon-photon scattering. Both of these have NOT been observed and verified experimentally.
Moreoever, if you have followed this thread, we are STUCK in classical E&M and haven't made any progress in establishing even THAT! I certainly am not in the mood to bring in QED when it is not clear that the parties in question don't even know classical E&M.
Zz.

Sure. And that's why I stressed you are correct according to classical theory. However, it may be that some others have heard about light scattering by an electromagnetic field, and took it for a classical effect, and then it might be good for those to be told it isn't like that.

 

[EL]

QED predicts this as a higher order interactions. QED also predicts photon-photon scattering. Both of these have NOT been observed and verified experimentally.

Ok, but we can agree on it has been verified for electric fields right? Don't you think that's enough evidence for also regarding photon-magnetic field scattering and photon-photon scattering as verified?
(So I have heard diverging opinions about this: Some think that Delbrück scattering is "enough" of evidence, however I would be glad to hear if you don't agree with them (mainly because I've been doing some work on photon-photon scattering detection myself... ).)

 

[ZapperZ]

I interpret (and so did everyone else who responded) the OP of this thread as a question on classical E&M (light having E and B field components). It would have sounded different had it been on QED.

And I don't know if it has been verified for E fields. Unless I understood QED wrongly, you will only see appreciable effects for gamma photons. This is also true for any possible "photon collider", which is more often called "gamma-gamma collider". I WISH such things have been verified because it would shut up all of those people who claim there's no "photons".

Zz.

 

[jtbell]

So are you saying that Faraday was wrong and that the polarization of light won't be rotated by a strong magnetic field?

Show me the physics that Faraday is describing. And then show me the EXPERIMENTAL VERIFICATION of such an effect.
Zz.

Pinestone, note that Faraday rotation takes place when light passes through a medium that is subjected to a magnetic field. It does not (as far as I can tell) occur when light travels through a vacuum. Faraday rotation is caused by the magnetic field's effect on the medium, not on the light itself.

 

[EL]

I interpret (and so did everyone else who responded) the OP of this thread as a question on classical E&M (light having E and B field components). It would have sounded different had it been on QED. And I don't know if it has been verified for E fields.

Ok. I interpreted it as a question about what can happen in reality, and in reality scattering of photons by an electric field (Delbrück scattering) has been verified! (Don't have the reference right now though.)
But I want to stress that the cross section for this process is extremely tiny, and it has nothing to do with this Faraday rotation which only occurs in a medium.
In summary, I get your point, and I agree with you that according to classical theory there is no interaction between EM-fields in vacuum.

Unless I understood QED wrongly, you will only see appreciable effects for gamma photons.

Well, it helps to have high energy photons, but it's not necessary. It could be enough to have large fields. (E.g. see http://www.arxiv.org/abs/hep-ph/0510076 )

 

[pinestone]

And I can show you where using a different dielectric medium where this will NOT occur. Why? Because it depends ON THE MATERIAL! Try it! I'll suggest one: a photonic band gap material! Use light with energy LESS than the size of the photonic band gap. Apply as much magnetic field as you want. You'll NEVER get the light to be "deflected".
Learn condensed matter physics, especially optical transmission in solids, before you proclaim such a thing.
Zz.

That is exactly what I try and do. I'll refrain from generalizations after this post, and be much more specific with my comments. Thanks again for the information.