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Manipulating light electro/magnetically

  1. Sep 23, 2010 #1
    Hi Guys,

    Sorry if this is a daft question, but....

    if light is a form of electromagnetic radiation (as we're all taught) then is is possible to manipulate it with magnets?

  2. jcsd
  3. Sep 23, 2010 #2
    Generally the problem is, that light doesn't have mass to manipulate, of course according to Einstein gravity can bend light
  4. Sep 23, 2010 #3
    Not directly.

    But it is possible to modify some materials with magnets (or magnetic fields), such that the material's effect on light is varied according to the magnet's influence.
  5. Sep 23, 2010 #4


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    One simple answer to the OP's question is that the classical equations of electromagnetism are completely linear, so a magnetic field (or an electric field) has no influence on light - the light waves just propagate right through it. In a medium, as Dr Lots-o-watts said, then the equations become non-linear so there can be an interaction between light and a magnetic field.
  6. Sep 23, 2010 #5


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    A good example of light manipulated by magnetic field in a medium is the Faraday Effect.

    Also, at REALLY high energies, EM equations become non-linear even in vacuum, but that's quantum electrodynamics already, and way outside of this scope.
  7. Sep 23, 2010 #6
    When light scatters in our atmosphere doesn't that have something to do with the E and B fields affected by the nitrogen molecules?
  8. Sep 23, 2010 #7
    Just curious, and with respect to the OP's question...
    Is it possible to manipulate a magnetic field in "free space" such that there WOULD be an effect on photons?
    That is, pulsation, rotation, etc... of that magnetic field.

    Note: What I mean by "free space" in this context is the magnetic field outside of a medium.

    Likely the answer is no, just curious.

    Similarly, if one had a very fast rotating laser beam going through a very fast counter-rotating magnetic field, would there be any difference?
  9. Sep 23, 2010 #8

    As K^2 says, with insanely high field of gamma rays, it may be possible to alter properties of vacuum itself, but this has not been verified experimentally to my knowledge.

    What is standard is that photons can become mass (which could affect a third-party photon) through pair creation, but even this needs a massive nucleus in the picture, if only to conserve momentum.

    What is on the forefront of research is that (extremely high energy density) photon-photon collisions seem to have created mass (again by pair creation). But again, this needed the presence of electrons, acting essentially as a mirror, emitting bremsstrahlung photons in response to the incident beam and colliding with it.

    As far as I know, there is no standard, bullet proof, independently verified, experimental evidence that photons can see each other.

    Remember that a magnetic field is also nothing but photons, like light (which is also a magnetic field right?
  10. Sep 24, 2010 #9
    Then why can I bend B field lines with another magnet . Are we saying photons affect other photons .
  11. Sep 24, 2010 #10


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    You don't "bend B field lines with another magnet" . The result of having two magnetic fields is simply the vector sum of the two fields. They have no impact on each other.
  12. Sep 26, 2010 #11


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    And electron-positron creation/annihilation processes don't verify non-linearity of EM field?
  13. Sep 26, 2010 #12
    Standard pair creation needs a nucleus, which is mass, to balance momentum.

    Pair creation from what seems to be colliding photons only is very recent. And even these experiments need electrons (mass) in the picture:
    "Possibility of Prolific Pair Production with High-Power Lasers", Phys. Rev. Lett. 101, 200403 (2008)

    What seems to be still missing to experimentally prove a non-linear vacuum is pair production from two independent photons in vacuum, without any help from any mass.

    I'm not sure how all this fits in with photons being bosons however.
  14. Sep 27, 2010 #13
    I hope you have had a good weekend!

    Thank you for the many interesting replies. I didn't realise the topic would generate this much discussion.

    Karoka, electrons have very little mass from what I remember, but they are highly influenced by an em field, ok they are charged, but if gravity can bend light (I think this is the gravitation lensing effect some astronmers us to look beyond a heavy object) wouldn't this suggest that photons are either:

    1) pulled in by a mass towards the centre of the same mass, or;
    2) pulled towards a mass as a result of other particles that are 'falling' towards the mass colliding with the photons and altering their path as a result?

    Dr Lots-o'watts, altering a material's optical props using magnets is sort of , well, like 'cheating'. I agree to what you're saying tho'.

    If a magnetic field (electric or otherwise) is simpley a region of photons of a different kind, then if I had 2 lasers,ie. 2 sources of photons of identical properties, then if I were to place them at an angle where they intersect, shouldn't I expect to see the 2 beams and also see photons break away from the beams in a manner that would fit statistical modelling of collisions?

    Or to put another way, the magnetic photons and laser photons are different, agreed, so if I were to use 2 identical lasers an cause an interesection between the 2 beams, then i would expect to see some of the photons to deviated fromt he original path of the 2 parent lasers.

    I think it was Rutherford that did something similar with and alpha source and gold leave. He was able to predict mathematically the number of alpha particles that would bounce back off the gold leaf.

    Essentially doing so would indicate collision/interactions of sorts.
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