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Gamma rays in a magnetic field

Charged particles are deflected in a magnetic field so I can understand from this point of view why gamma rays (or any other electromagnetic wave for that matter) would not be deflected in a magnetic field.

But a gamma ray is an electromagnetic wave so consists of electric and magnetic fields. So wouldn't the magnetic field interact with the magnetic field produced by the wave and so deflect it?

Not really important but I am just intrigued. Thanks :smile:
Reply 1
Avatar for 3nTr0pY
3nTr0pY
3
This is a really good question. It's late now and giving a proper answer will definitely take some thought so hopefully I can write one up tomorrow. Would be interested to see if anyone has any particular thoughts on this...
It's late at night so this might be wrong, but here's what I think.

I say a magnetic field will affect a light wave - you can affect the polarization in this way - but it will not deflect it. In the light wave we have an electric field oscillating at a right angle to an oscillating magnetic field. We also have something called the Poynting vector (http://en.wikipedia.org/wiki/Poynting_vector), the vector product of both fields, which points perpendicular to both fields and gives the direction of energy propagation - ie. the direction of the light ray. Applying an external magnetic field will be a straightforward vector addition to the magnetic component of the light ray, but the light wave's electric and magnetic fields still remain perpendicular to one another therefore the Poynting vector still points in the same direction as before.
(edited 11 years ago)
Reply 3
Avatar for 3nTr0pY
3nTr0pY
3
I'm confident SnoochToTheBooch is right about it not being deflected.

What needs to be remembered is that the gamma ray isn't the source of the electromagnetic field, it is the electromagnetic field. An electromagnetic interaction would require the interaction of an electromagnetic field with a charge of some kind - but no charge is present.

With regards to polarisation, I'm not sure it's fair to say that the polarisation of the original photon changes. Instead you would expect the photons from the new magnetic field to add up linearly with the original photons in the relevant region. As soon as the original photons, which constitute the em wave, leave the area with the magnetic field, I would expect them to retain their initial polarisation state. That's what I reckon anyway.



Finally, I suppose there would be a tiny deflection due to general relativity. An applied magnetic field has energy and this energy would bend the photon's path due to its gravity. This effect would be negligibly tiny though.
(edited 11 years ago)

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