# Forces affecting the path of a photon

1. Jun 11, 2006

### professor

could anyone be so kind as to provide a list for me, im attempting to better a formulate a further question, but this list would be greatly helpful in my understandign of what i am trying to ask.

the two i can easily think of are:
1.gravity
2.magnetism

can anyone correct me if either should be incorrect, and let me know of any others they should happen to think of.

ohh yes, a few more questions i might as well ask while im at it: a phton is infact the most energatic particle per mass amount right?

and also, why does light not all collapse into laser like rays assuming that photons have an event-horizon of a sort... nevermind, they must not, but at one point i would expect if they got close enough... no max speed = max gravity to capture another photon, nevermind that question- ill leave my thoughts up so you can see what i was getting at if you have any insightfull ideas fo me.

2. Jun 11, 2006

### wywong

There are only 4 known forces in nature - gravity, electromagnetic, strong and weak. The first two of course do affect the path of photons. The last two, as far as I know, do not interact with photos, and their effect outside the atom nucleus can usually be ignored.

Photons, and some other particles like gluons, have no resting mass. So 'per mass' is inapplicable.

Can't help here as I cannot following your thinking. Perhaps a popular book on quantum physics may help.

Wai Wong

3. Jun 11, 2006

### Hootenanny

Staff Emeritus
Excuse me for asking, but why would the electromagentic force affect the path of a photon?

4. Jun 11, 2006

### Parlyne

It wouldn't.

However, the weak force would, because the $$W^{+}$$ and $$W^{-}$$ bosons carry electrical charge.

5. Jun 11, 2006

### wywong

Sorry if this is beyond the scope of this group. In ordinary circumstances, the EM force doesn't. But the photon is not always a photon; it can split into an electron and positron spontaneously. Usually, they recombine before they can be observed. However, under extreme EM field, the two particles may follow different paths and thus cannot recombine. A spliting, rather than bending, results. See

Wai Wong

Last edited by a moderator: Apr 22, 2017
6. Jun 11, 2006

### Hootenanny

Staff Emeritus
Yes, but the EM force only exerts a force on the two particles, not the photon (because it no longer exhists). Also, to me knowlage this phenomena has never been conclusively observed.

7. Jun 11, 2006

### professor

the electromagnetic force would not affect the photons, because they are not charged, i see that much now, i also see that the splitting which may or may not happen would have an affect on the path of the photon, and perhaps lead to the seperation of it temporarily,

but as another question: why would the weak force affect a photon, as explained above it is because of more charged particles, so a charged boson affects the photon, but not a charged fermion?

Last edited: Jun 11, 2006
8. Jun 12, 2006

### Claude Bile

Atoms generate photons via spontaneous and stimulated emission - Atoms absorb photons - Atoms can also cause photons to reflect and refract (there are several threads as to why/how this happens).

What force causes these interactions? I think it's fairly safe to rule out gravity and both the nuclear forces. The obvious answer is therefore the electromagnetic force.

One could therefore conclude that the electromagntic force affects photons quite strongly.

Claude.

9. Jun 12, 2006

### Parlyne

Claude, all the examples you are giving have photons directly interacting with charged particles. If a photon is in a region with non-zero electric and/or magnetic fields, but no charged particles, it should be unaffected, as the E&M fields are essentially also photons and photons don't interact with each other (at least not directly).

Professor, a photon will interact with any charged particle, fermion or boson.