# Can a Photon be deflected by Magnetic and Electric Field?

1. Feb 1, 2010

### utsav55

1. The problem statement, all variables and given/known data
Can a Photon be deflected by Magnetic Field and Electric Field?

2. Relevant equations

3. The attempt at a solution
Photon cannot be deflected by either, as it has no electric charge.

2. Feb 1, 2010

### Zhivago

Correct, the photon has no charge or mass (although it has a spin!), so it can't be deflected. The photon itself is the propagation of a sinusoidal magnetic and electric field.

3. Feb 1, 2010

thank you

4. Feb 1, 2010

### Count Iblis

Almost correct. Heisenberg and Euler were the first to give the correct answer to this question http://arxiv.org/abs/physics/0605038" [Broken] in 1936.

A modern treatment can be found http://arxiv.org/abs/hep-ph/9806417" [Broken]

Last edited by a moderator: May 4, 2017
5. Feb 1, 2010

### chrispb

This question amounts to whether photon-photon scattering can occur, I think. I'm no expert, but I see no reason why the answer should not include this graph: http://colinfahey.com/eclectic_images_2002/gg-scat.jpg

Obviously, there's no tree level diagram cause there's no A^4 in the QED lagrangian, but I can't see why the above diagram wouldn't be allowed.

6. Feb 1, 2010

### Count Iblis

That's right and this gives rise other effects as well. If you connect one of the photon lines to a real electron, you get the diagram that describes the splitting of a photon due to interaction with a charge (rather than mere Compton scattering). Computing the amplitude is an exercise in the book by Itzykson Zuber.

7. Sep 2, 2011

### Cybertib

I would like to catch your attention to the following recent article.
http://prl.aps.org/abstract/PRL/v106/i19/e193003

The abstract is the following.

"We report the direct observation of the nonreciprocity of the velocity of light, induced by electric and magnetic fields. This bilinear magneto-electro-optical effect appears in crossed electric and magnetic fields perpendicular to the light wave vector, as a refractive index difference between two counterpropagating directions. Using a high finesse ring cavity, we have measured this magnetoelectric nonreciprocity in molecular nitrogen at ambient temperature and atmospheric pressure; for light polarized parallel to the magnetic field it is 2η∥exp⁡(N2)=(4.7±1)×10-23  m V-1 T-1 for λ=1064  nm, in agreement with the expected order of magnitude. Our measurement opens the way to a deeper insight into light-matter interaction beyond the electric dipole approximation. We were able to measure a nonreciprocity as small as Δn=(5±2)×10-18, which makes its observation in quantum vacuum a conceivable challenge."

It has been reported as being a first experimental evidence of a possibility for photon-photon collision, here.

http://www.physorg.com/news/2011-05-when-the-speed-of-light.html

Cheers,
Thibault

8. Sep 6, 2011

### rude man

A lot of this nonsense about photons doing one thing when you're looking at them and another if you're not is explained by the interaction of light and photons. In other words, you need light to see so yeah, they act differently if they are somehow sensitive to light.

(Another bit of nonsense is the Schroedinger's Cat thing. Schroedinger intended this as an illustration of some of the absurdities promulgated back then in quantum mechanics. But most peole seemingly took him literally and believe that the poor cat really IS neither dead nor alive until the box is opened.)

Am I boring anyone yet? :-)