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sqljunkey
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Can an everyday magnet disturb a ray of light. I have seen many answers online saying no, and some saying yes, but only if the magnetic field is large enough.
Not in free space, however powerful the magnet. The same applies to crossing beams of light; no interaction.sqljunkey said:only if the magnetic field is large enough
sysprog said:The magnetic field of an 'everyday magnet' is not energetic enough to produce gravitational effects sufficient to 'disturb' a ray of light
At high enough energies the EM Force can produce 'gravitational effects', including bending light rays, by curving spacetime.davenn said:Huh??sysprog said:The magnetic field of an 'everyday magnet' is not energetic enough to produce gravitational effects sufficient to 'disturb' a ray of light
Magnetic fields don't produce gravitational fields
Mass does
The rest of that post includes material (e.g. tensor field equations) that I think exceeds 'B' level thread standards.Just looking at general relativity: the answer to the question: "Can a light be bent by a magnetic field?" is yes it can be bent due to the curvature of spacetime produced by a strong magnetic field. I can give a very short answer why, without going into too much detail, how the resulting bent geodesics might look ...
I suspect you misunderstand the answers in that link because the poster goes on to describe mass gravitational effects NOT magnetic fieldsysprog said:At high enough energies the EM Force can produce 'gravitational effects', including bending light rays, by curving spacetime.
From: a stackexchange post by user M. J. Steil (Sep 5 '16 at 21:02):
The rest of that post includes material (e.g. tensor field equations) that I think exceeds 'B' level thread standards.
sophiecentaur said:However, in some substances, the fields due to an intense beam of light can cause non-linear effects and the fields can affect each other.
sqljunkey said:You mean the Zeeman effect by that? https://en.wikipedia.org/wiki/Zeeman_effect ,
sqljunkey said:You mean the Zeeman effect by that? https://en.wikipedia.org/wiki/Zeeman_effect ,
An electromagnetic field curves spacetime by its energy-momentum tensor. This tensor sources gravity in Einsteins theory of general relativity.davenn said:
haushofer said:An electromagnetic field curves spacetime by its energy-momentum tensor. This tensor sources gravity in Einsteins theory of general relativity.
This effect is, however, very weak.
I think I introduced some confusion when I made reference to 'gravitational effects'. @davenn correctly pointed out that gravitational effects are due to mass. You correctly made reference to EMF spacetime curvature being due to the energy-momentum tensor. At very high energies, this 'very weak' effect is no longer so weak as to be negligible, but at ordinary energies, it is well-established that electromagnetic fields produce no observable bending of light.haushofer said:An electromagnetic field curves spacetime by its energy-momentum tensor. This tensor sources gravity in Einsteins theory of general relativity.
This effect is, however, very weak.
I was under the impression that observations of neutron stars and pulsars had been accounted to evince the EMF contribution to spacetime curvature, i.e. the observed mass doesn't account for all of the observed curvature in their vicinity, but with inclusion of the EMF energy-momentum tensor it does.ZapperZ said:Instead of describing it as "... very weak.. ", try "...has never been observed before...". This is clearer to the general public, and probably will straighten out the OP who may have read similar statement and thinks that this has been verified.
Zz.
sophiecentaur said:However, in some substances, the fields due to an intense beam of light can cause non-linear effects and the fields can affect each other.
The magnetic field is not even slightly disturbing the light ray itself; it's strongly affecting the material through which the light is passing.sqljunkey said:I get it now. I guess one could argue that since an "everyday magnet" is surrounded by air molecules usually, which is a medium , there would be slight disturbance in the light ray due to the Faraday Effect.
Which in turn disturbs the light yes.sysprog said:The magnetic field is not even slightly disturbing the light ray itself; it's strongly affecting the material through which the light is passing.
In other words, it's affecting the geodesic by which the light follows, yes?sysprog said:it's strongly affecting the material through which the light is passing.
Yes, just as a ferrometallic metal mirror being warped by a magnet could change the path of reflected light, but that wouldn't be EMF bending light -- other than under certain very limited exceptional conditions, EMF cannot bend or otherwise affect light.sqljunkey said:Which in turn disturbs the light yes.
No. Those are not other words for the same thing. The geodesic in GR is referential to spacetime curvature; not to such things as refractive index or polarization characteristics of semi-transparent materials.Comeback City said:In other words, it's affecting the geodesic by which the light follows, yes?sysprog said:it's strongly affecting the material through which the light is passing.
Let me clarify... I was referring to the original question, not anything to do with the Zeeman effect or the Faraday effect. Your quote from the stack exchange post seems to say that the magnetic field affects the geodesic which light follows... is that correct?sysprog said:No. Those are not other words for the same thing. The geodesic in GR is referential to spacetime curvature; not to such things as refractive index or polarization characteristics of semi-transparent materials.
Yes. That's possibly-inferentially-observably true only in very exceptional high-energy conditions. An 'everyday magnet', as in the original question, cannot bend light.Comeback City said:Let me clarify... I was referring to the original question, not anything to do with the Zeeman effect or the Faraday effect. Your quote from the stack exchange post seems to say that the magnetic field affects the geodesic which light follows... is that correct?
Not sure. The waves will both have E and H fields so I don't know how you would classify it. (But why bother if it doesn't contribute to the understanding?)sqljunkey said:You meant Faraday Effect instead of the Zeeman effect?
28–3 Electromagnetic mass
Where does the mass come from? In our laws of mechanics we have supposed that every object “carries” a thing we call the mass—which also means that it “carries” a momentum proportional to its velocity. Now we discover that it is understandable that a charged particle carries a momentum proportional to its velocity. It might, in fact, be that the mass is just the effect of electrodynamics. The origin of mass has until now been unexplained. We have at last in the theory of electrodynamics a grand opportunity to understand something that we never understood before. It comes out of the blue—or rather, from Maxwell and Poynting—that any charged particle will have a momentum proportional to its velocity just from electromagnetic influences.
Let’s be conservative and say, for a moment, that there are two kinds of mass—that the total momentum of an object could be the sum of a mechanical momentum and the electromagnetic momentum. The mechanical momentum is the “mechanical” mass, ##m_{\text{mech}}##, times ##v##. In experiments where we measure the mass of a particle by seeing how much momentum it has, or how it swings around in an orbit, we are measuring the total mass. We say generally that the momentum is the total mass ##(m_{\text{mech}}+m_{\text{elec}})## times the velocity. So the observed mass can consist of two pieces (or possibly more if we include other fields): a mechanical piece plus an electromagnetic piece. We know that there is definitely an electromagnetic piece, and we have a formula for it. And there is the thrilling possibility that the mechanical piece is not there at all—that the mass is all electromagnetic.
Yes, a magnet can indeed bend a ray of light. This phenomenon is known as the Faraday effect, and it occurs when a magnetic field is applied to a transparent material such as glass or plastic.
The Faraday effect is caused by the interaction between the magnetic field and the electrons in the material. When light passes through the material, the magnetic field causes the electrons to move, which in turn changes the polarization of the light and causes it to bend.
The amount of bending depends on the strength of the magnetic field and the material it is applied to. In most cases, the bending is very small and not noticeable to the naked eye. However, with strong magnetic fields and certain materials, the bending can be significant.
The Faraday effect can occur with any magnet, but it is more pronounced with strong magnets such as neodymium magnets. The material it is applied to also plays a role in the amount of bending that occurs.
Yes, the Faraday effect has many practical applications in fields such as telecommunications, optics, and data storage. It is used to modulate light signals, create optical isolators, and even measure magnetic fields.