Photon Question

[cwes99_03]

No. While the collision of charged particles may produce a photon, no collision is needed. All that is needed is for a particle with electrons to pass through a sufficient electric field to excite one of the valence electrons to change down an energy state. The type of light produced is equal to the difference between the energy states before and after the transition (at least as far as low end spectrum light production goes). To produce higher levels of light radiation (such as gamma), generally an atom has to be split to release enough energy.

However, two colliding particles that aren't perfectly elastic will also produce light (which maintains the energy balance before and after the collision.)

Check out the Raman Effect for more information on how light interacts and is produced with particles. It is only a tiny part, but I think it will show you that there are lots of different ways for light to be produced.

[Qfwfq]

It depends on what one means by the word 'collision'. In modern terminology, any interaction that isn't between two particles in a bound state. Of course, even in a bound state there are virtual bosons...

[Farsight]

I guess two magnets can "collide", and interact without actually touching each other.

[Erasmus00]

Originally Posted by cwes99_03

All that is needed is for a particle with electrons to pass through a sufficient electric field to excite one of the valence electrons to change down an energy state.

It depends also on what you mean by particle. I was thinking of fundamental particles, (protons, neutrons,electrons) which take high energies to excite their substructure. Also, in the absence of any field in the tube, the electrons aren't going to be excited by anything but the field of the other atom, i.e. a collision.
-Will

[cwes99_03]

Quite right, I think I latched on to the use of the word molecule in the original question.

[Little Bang]

If we look at the reaction of hydrogen with oxygen, there are photons produced I guess becase of the excitation of the valence electrons. Correct me if I'm wrong but that should mean that some mass was converted to a photon. Now we can use electrolosis to break the hydrogen and oxygen back apart. Does this mean that some energy has been converted into mass?

[cwes99_03]

What do you mean by reaction?

If you are talking about the chemical reaction between Hydrogen and Oxygen to form water, then I'd say this needs to be in the chemistry forum not physics and mathematics.

Also, if it should be moved to chemistry, you'll have to back up your claim about their being a photon produced.

[Qfwfq]

The reaction is certainly exothermic though I'm not sure of details, photons might likely be emitted indirectly by deionization.

Originally Posted by Little Bang

Correct me if I'm wrong but that should mean that some mass was converted to a photon. Now we can use electrolosis to break the hydrogen and oxygen back apart. Does this mean that some energy has been converted into mass?

There certainly is conversion between rest energy and thermal/luminous energy. In detail, however, the rest energy (or mass) of the atoms and molecules is determined in part by the energy levels of the orbitals, which in turn is the sum of kinetic and potential energy of the electrons. This is the only part of the rest energy that changes.

Of course, compared to nuclear reactions, chemical ones involve very tiny variations of mass in proportion to that of the reagents.

[cwes99_03]

Heat is released in the form of radiation. However the transference of mass to energy is put into phononic energy (vibration in the degrees of freedom of the molecule, or in making the molecule move faster). Therefore the reaction itself does not produce radiation (light) put creates a system that has to pass on it's energy to other systems that have less energy.

Again if this is what you are discussing this needs to be moved to the chemistry forum.

[Qfwfq]

I don't see it as necessarily chemistry.

I suppose you mean for the specific case of hydrogen combustion, that all light comes from incandescence, I know that for many flames there is some direct emission of photons, which can give the flame colours rather than a blackbody spectrum.