What is a photon, if light can be emitted from atoms?

Question

Knowing that lasers work by exciting atoms until they emit light, what is a photon if it can come out of an atom? Since a laser doesn't ionize the atoms, it can't be an electron. And I can't think of what else it might be.

Answer 1

Its a vibrating electric field , magnetic field, electric field, magnetic field....



Lasers can ionise some atoms but you are right in that such ionisation is not relevant to the formation of photons.



Photons come out of atoms when an electrons loses energy. As it loses energy the electron shifts ( we like to think, downwards). That shift seems to shake the space around. That bit of shake, moves the next bit of space, which moves the next bit and the moving bit IS the photon. It really isn't anything, just a shifting patch of space - a piece of energy.



This is really, really hard. If you keep thinking on it and working on it, then you might be the one to finally explain what is really going on to the rest of us. I'm not being smart about this - nobody knows how to put it any better than I just did and all know that that wasn't very helpful.

Good luck

Answer 2

A photon for all practical purposes is a quanta of electromagnetic energy.



The energy difference between bound states must be carried away, and the process is by the release (or perhaps creation is more accurate) of a photon, which carries away that exact energy.



Lasers don't exactly excite atoms until they emit light so much as they force atoms in to the same state and then cascade off the energy by releasing a large amount of photons simultaneously. You're right though, it does not ionize (if it did then it would be reasonable to think its an electron).



Maybe what you're getting caught up on is you're forcing in your mind a conservation of particle number. In the real world, you have 2 apples and 3 bananas you throw them around and you'll still end up with 2 apples, 3 bananas. In particles, you toss around some electrons, neutrons and protons you don't always have the same things. You can end up with pions, neutrinos, and photons among others. Colliders between two protons can actually produce a 3rd proton and a 4th particle -- anti-proton. It depends on what energy is involved here. Since photon is 0 mass, it can be produced any time that an electromagnetic process is involved that results in the change of energy and does not alter charge (this would require the weak force, or the energy is carried away in electron anti-electron neutrino pairs, for example).

Answer 3

Photons are zero mass packets of energy (proved by Albert Einstein when he solved the mystery behind the photoelectric effect). Atoms release photons, because as an electron moves from a high energy state to a low energy state, it releases one photon- only one. The wavelength of the photon depends on how many energy levels the electron "drops". Now, keep in mind, a photon, or a "quanta", is also a wave, hence the wave particle duality. If you want to learn more, pick up a book on quantum mechanics, very interesting, confusing, frustrating and rewarding.

Answer 4

The atom loses energy. Usually this is a result of an electron dropping to a lower energy state. PartB: an atom can emit light in certain wavelengths governed by the type of atom, how energetic the electron was, and how many levels it dropped. Different types of atoms can emit photons in different, but discreet, wavelengths. This is the source of 'emission lines' in spectroscopy. Scientists using this instrument can tell you what kind (or kinds) of atoms emitted the light, and what kind (or kinds) of atoms were between the light source and the observer. The second bit of data comes from absorption lines.

Answer 5

Yeah Rex, I think I can put it better.



A photon in essence is a Electromagnetic wave. When you excite an electron, and give it a certain amount of energy, that electron will instantly release that energy. The reason this occurs is that electrons can only exist in certain energy levels with particular energys. Once they obtain an energy above and beyond that energy level, they relase that energy in the form of a photon, which is a electromagnetic wave.