Timeline for Why does light bend?
Current License: CC BY-SA 3.0
15 events
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| May 8, 2016 at 15:27 | comment | added | garyp | Guys, you are getting of the rails here. It's up to the OP to decide whether or not this answers the question. | |
| Oct 13, 2015 at 7:26 | history | edited | Fabrice NEYRET | CC BY-SA 3.0 |
added 12 characters in body
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| Oct 12, 2015 at 8:39 | comment | added | Fabrice NEYRET | About photons in general: it's dangerous to think of them as if they were really particles. The only quantisations in qEM is the chunk of energy and the unitary emission/absorption. Extrapolations yield many undue paradoxes (e.g. if you accelerate in a field, you can see more photons than at rest). QM is very strange for the us humans, so it's crucial to never overstate (i.e. extrapolate) properties. Moreover, single isolated transitory photon vs a full field at equilibrium are very different objects. | |
| Oct 12, 2015 at 8:32 | comment | added | Fabrice NEYRET | 4- To wrap up: 1: speed of light in material is a macroscopic effect of interaction between direct EM field and reacting (because free-charges or dipolar material) retarded (because of mass of moving charged) EM. 2: Huygens principle show how simple interferences make one front building the other. This is the cause of light propagating straight in a constant medium, and the cause of tilting at refraction. Same for mirror reflection: classical explaination is deceiving when you consider mirrors look like mountains at micro-scale. Fronts re-compose only in the far-field (ie, higher scale). | |
| Oct 12, 2015 at 8:26 | comment | added | Fabrice NEYRET | 3- Still the base idea of what you say (reemission from the front) can be saved if you do it on waves: this is the very Huygens principle. | |
| Oct 12, 2015 at 8:24 | comment | added | Fabrice NEYRET | 2- No absorption/reemission here. proof: all polarisation and intrication effects are conserve through optics (otherwise large interferometers like the VLT wouldn't work ;-) ). These are elastic interactions. | |
| Oct 12, 2015 at 8:23 | comment | added | Fabrice NEYRET | 1- It's really dangerous to think in terms of photons since they can be very virtual when it's about waves, and you could event get false results. Typically in refraction you have an EM field plus a retarded reactive EM field and what you see is their superimposition. Try to give a meaning to photons in such a result. :-D | |
| Oct 11, 2015 at 19:49 | comment | added | Jabavu Adams | I find the above diagram of the wave-fronts useful, but one could still ask "Why does the wave-front bend?". Am I right in assuming that if we look at any point across the wave-front that the light at the point is slowing down as it enters a more dense medium, or speeding up as it enters a less dense one. This due to photons hitting constituents of the medium and having to be absorbed and then re-emitted? | |
| Oct 8, 2015 at 22:23 | comment | added | Fabrice NEYRET | This is reasonning, this is not seeing for one, a ray, for another, fronts, for yet another, time or energy. 2+2 and 6-2 are both 4. Shown operations are different. | |
| Oct 8, 2015 at 22:16 | comment | added | gented | Again, the phenomenology is the same. The angles and tilts that you see in optic-based explanations are nothing but the boundary conditions on the wave equation between two surfaces (which is why the wavelength and the direction of propagation changes). | |
| Oct 8, 2015 at 20:24 | comment | added | Fabrice NEYRET | I was not speaking of how they where found, but how they are explain (phenomenologicaly). In most optic-based explanations you see rays and tilt angles, and no more. I do agree that the wave explanation is more constructive. Yet, you'll have to explain why celerity and wavelength change, but it's doable (at least for university students in sciences, not for pupils or litterature students :-) ). | |
| Oct 8, 2015 at 20:18 | comment | added | gented | That's indeed why I disagree: the didactic and mental representation are exactly the same because that's how you derive Snell's law. Claiming they are two didactic different ways to achieve the same result is hiding where they come from, in my opinion. | |
| Oct 8, 2015 at 20:11 | comment | added | Fabrice NEYRET | The result is obviously the same. But the diagram and didactic and mental representation are not the same using the wave form or the ray form. This is pretty classic in physics that you can watch a same phenomena under 2 or 3 very different facets (I would say it's one of the best beauty of physics understanding). E.g. here, we could also have taken the Fermat point of view about path of minimal energy. | |
| Oct 8, 2015 at 20:08 | comment | added | gented | The wave aspect is exactly Snell's law. | |
| Oct 8, 2015 at 19:50 | history | answered | Fabrice NEYRET | CC BY-SA 3.0 |