Timeline for What determines the direction of a photon emitted by an electron?
Current License: CC BY-SA 4.0
23 events
| when toggle format | what | by | license | comment | |
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| Sep 15, 2018 at 15:05 | comment | added | BioPhysicist | @ManudeHanoi that is fine. You never specified in your above comments this is what you meant by "free". All of this would have been avoided if you had just said what you meant by free. No one here is wrong, just talking about two different things. Typically in physics, free means no interactions, and the electrons you speak of would be not bound to any atoms. But if you want free to mean not bound to atoms, then specify this rather than getting upset with people who are just using different terminology than you. | |
| Sep 15, 2018 at 14:50 | comment | added | Manu de Hanoi | @AaronStevens Ive used and been taught in high school that metals conduct electricity because they have free electrons. Free meaning not being bound to a particular atom. | |
| Sep 15, 2018 at 13:46 | comment | added | BioPhysicist | @ManudeHanoi I have to agree with JonCuster here. Acceleration is needed for radiation emission. By definition, "free" means no other interactions. So free electrons can't accelerate and emit photons. Of course truly free electrons can't exist, but that doesn't mean the idea is useless. It's like when we assume frictionless surfaces or neglect air resistance. The assumptions aren't true, but they are close enough to reality that they are still useful with the bonus of being easier to work with. | |
| Sep 15, 2018 at 12:12 | answer | added | anna v | timeline score: 3 | |
| Sep 15, 2018 at 12:06 | comment | added | Gabriel Golfetti | Are you familiar with the computation of QFT propagators? | |
| Sep 15, 2018 at 11:43 | answer | added | flippiefanus | timeline score: 1 | |
| Sep 14, 2018 at 17:11 | comment | added | PM 2Ring | It is better to think of a photon being absorbed or emitted by the whole atom rather than by the electron. But even so, for spontaneous emission by a free atom nothing determines the emission direction, all directions have equal probability | |
| Sep 14, 2018 at 17:11 | comment | added | Jon Custer | @DavidWhite - and that requires shaking the electrons around - they are only propagating 'freely' between the undulators, and in the undulators they are forced to, well, undulate... | |
| Sep 14, 2018 at 15:46 | comment | added | David White | @JonCuster, there is, of course, the free-electron laser. See en.wikipedia.org/wiki/Free-electron_laser | |
| Sep 14, 2018 at 15:38 | comment | added | Cosmas Zachos | Behold. | |
| Sep 14, 2018 at 15:24 | comment | added | Manu de Hanoi | @CosmasZachos there is no free electron in the universe according to your definition. Therefore your definition of "free electron" is useless. You should know that's not what we mean by free electron | |
| Sep 14, 2018 at 15:22 | comment | added | Cosmas Zachos | @ManudeHanoi Absolutely. Acceleration is the result of an interaction; "free" is an idealization where such interactions are ignorable. | |
| Sep 14, 2018 at 15:20 | comment | added | Manu de Hanoi | @CosmasZachos yeah yeah, then if all it takes is for a force to apply to an electron to make it not free, then there is not a single free electron in the universe. Again from wiki: "Electromagnetic waves are emitted by electrically charged particles undergoing acceleration." | |
| Sep 14, 2018 at 15:17 | comment | added | Manu de Hanoi | I dont know why u claim that free electrons cant emit photons. To emit photons u need a quick change in the electric field, a moving electron can do that | |
| Sep 14, 2018 at 15:14 | comment | added | Manu de Hanoi | @CosmasZachos from wikipedia "Cyclotron radiation is emitted by all charged particles travelling through magnetic fields, not just those in cyclotrons." | |
| Sep 14, 2018 at 15:04 | comment | added | Cosmas Zachos | @ManudeHanoi that's just it: the particles are accelerated by the magnetic field: they are effectively absorbing photons and are very unfree indeed. | |
| Sep 14, 2018 at 14:58 | comment | added | Manu de Hanoi | @JonCuster what about cyclotron radiation? en.wikipedia.org/wiki/Cyclotron_radiation | |
| Sep 14, 2018 at 14:43 | comment | added | Jon Custer | @ManudeHanoi - sure, when they hit something. A freely propagating electron does not emit photons. | |
| Sep 14, 2018 at 14:42 | comment | added | Manu de Hanoi | @JonCuster I believe electrons in a cathode ray tube can emit photons (x ray) | |
| Sep 14, 2018 at 14:24 | comment | added | Persian_Gulf | actually, the photon direction is random in the spontaneous emission. and there is no rule! | |
| Sep 14, 2018 at 14:14 | answer | added | Manu de Hanoi | timeline score: -1 | |
| Sep 14, 2018 at 14:08 | comment | added | Jon Custer | (1) A free electron does not emit photons. (2) An electron attached to an atom is not a point entity. | |
| Sep 14, 2018 at 14:01 | history | asked | uKER | CC BY-SA 4.0 |