Itoero Posted October 7, 2017 Share Posted October 7, 2017 I read the kinetic energy of a photon goes to infinity when a photon reaches c. Is that possible?( E=hf ) Does the wavelength/frequency of a photon changes depending on the medium? Link to comment Share on other sites More sharing options...
Strange Posted October 7, 2017 Share Posted October 7, 2017 32 minutes ago, Itoero said: I read the kinetic energy of a photon goes to infinity when a photon reaches c. Is that possible?( E=hf ) As a photon always moves at c then that is obviously wrong. Quote Does the wavelength/frequency of a photon changes depending on the medium? In the classical description the wavelength (and speed) changes which causes refraction. I don't think that is true in the quantum view - refraction is due to the interaction of the photons with electrons but they continue to move at c. Link to comment Share on other sites More sharing options...
J.C.MacSwell Posted October 7, 2017 Share Posted October 7, 2017 38 minutes ago, Itoero said: I read the kinetic energy of a photon goes to infinity when a photon reaches c. Is that possible?( E=hf ) Does the wavelength/frequency of a photon changes depending on the medium? If it's not at c, it's not a photon... Link to comment Share on other sites More sharing options...
Itoero Posted October 7, 2017 Author Share Posted October 7, 2017 8 minutes ago, Strange said: As a photon always moves at c then that is obviously wrong. If a photon travels through glass , does it move at c? Link to comment Share on other sites More sharing options...
J.C.MacSwell Posted October 7, 2017 Share Posted October 7, 2017 54 minutes ago, Itoero said: If a photon travels through glass , does it move at c? Yes. When it's moving, when it's a photon, it travels at c. Link to comment Share on other sites More sharing options...
Itoero Posted October 8, 2017 Author Share Posted October 8, 2017 18 hours ago, J.C.MacSwell said: Yes. When it's moving, when it's a photon, it travels at c. So a photon 'interacts' with particles in whatever medium it is and it always travels at c. Only the observable light can slow down and bend according to the medium . Correct? Link to comment Share on other sites More sharing options...
Strange Posted October 8, 2017 Share Posted October 8, 2017 1 hour ago, Itoero said: So a photon 'interacts' with particles in whatever medium it is and it always travels at c. Only the observable light can slow down and bend according to the medium . Correct? That is an odd/interesting way of putting it, but basically yes. We can only say anything about a photon when we detect it. And I suppose that is true for a classical wave as well. The difference is that we don't have to destroy a wave to observe it (e.g. you can see the path of light through smoke). Link to comment Share on other sites More sharing options...
Sensei Posted October 8, 2017 Share Posted October 8, 2017 You see laser path in smoke, because some laser photons hit molecule of smoke, and diffused in the all directions. Such photon is no longer part of laser beam. Link to comment Share on other sites More sharing options...
Strange Posted October 8, 2017 Share Posted October 8, 2017 5 minutes ago, Sensei said: You see laser path in smoke, because some laser photons hit molecule of smoke, and diffused in the all directions. Such photon is no longer part of laser beam. True but rather missing the point. Link to comment Share on other sites More sharing options...
Vmedvil Posted October 9, 2017 Share Posted October 9, 2017 (edited) The reason that photons seem to slow down in certain medium is for a time they become energy of a electron then are transmitted as the electron loses this energy. Light seems to slow due to this time repeatedly spent as electron energy. The light particle is never going slower than the speed of light but the electron that absorbs and transmit it does go slower than the speed of light. This is why you get the illusion that the light particle is going slower than the speed of light, but no those are the electrons. The interaction with electrons cause photon lag time it would be like having a 2.6 GHz processor run into a 1.1 GHz video card, despite being 2.6 GHz when running information through the video card it can only use 1.1 GHz this creates a disconnect in speed, you would ask? Why is my processor running so slowly, no that is your video card causing that because it is so slow only being 1.1 GHz. This in electrons is due to rest mass which photons have none causing them to move much more slowly. Edited October 9, 2017 by Vmedvil Link to comment Share on other sites More sharing options...
Itoero Posted October 10, 2017 Author Share Posted October 10, 2017 On 7-10-2017 at 5:24 PM, Strange said: In the classical description the wavelength (and speed) changes which causes refraction. I don't think that is true in the quantum view - refraction is due to the interaction of the photons with electrons but they continue to move at c. The inelastic scattering of photons (x or gamma) by electrons (or other charged particles) is called: Compton scattering. It results in a decrease in energy which increases its wavelength. This can happen because the energy of the photon is much larger then the binding energy of the atomic electron then the atomic electron acts like a free electron. You have also the inverse Compton effect where photons gain energy. Rayleigh scattering is the (mostly) elastic scattering of electromagnetic radiation by atoms or molecules which have to be much smaller then the wavelength of the radiation. Rayleigh scattering of sunlight in the atmosphere causes diffuse sky radiation, which is the reason for the blue color of the sky and the yellow tone of the sun itself. The red colour in the sky at sunset is due to the fact that when you receive photons from the sun, the photons have to travel through more of the atmosphere which is nearer to earths surface which makes it more dense. This removes a significant proportion of the shorter wavelength (blue) and medium wavelength (green) light from the direct path to the observer. The remaining light is therefore mostly of longer wavelengths(lower energy) and appears redder. https://en.wikipedia.org/wiki/Compton_scattering https://en.wikipedia.org/wiki/Rayleigh_scattering Link to comment Share on other sites More sharing options...
Strange Posted October 10, 2017 Share Posted October 10, 2017 4 minutes ago, Itoero said: The inelastic scattering of photons (x or gamma) by electrons (or other charged particles) is called: Compton scattering. It results in a decrease in energy which increases its wavelength. This can happen because the energy of the photon is much larger then the binding energy of the atomic electron then the atomic electron acts like a free electron. You have also the inverse Compton effect where photons gain energy. Rayleigh scattering is the (mostly) elastic scattering of electromagnetic radiation by atoms or molecules which have to be much smaller then the wavelength of the radiation. Rayleigh scattering of sunlight in the atmosphere causes diffuse sky radiation, which is the reason for the blue color of the sky and the yellow tone of the sun itself. The red colour in the sky at sunset is due to the fact that when you receive photons from the sun, the photons have to travel through more of the atmosphere which is nearer to earths surface which makes it more dense. This removes a significant proportion of the shorter wavelength (blue) and medium wavelength (green) light from the direct path to the observer. The remaining light is therefore mostly of longer wavelengths(lower energy) and appears redder. https://en.wikipedia.org/wiki/Compton_scattering https://en.wikipedia.org/wiki/Rayleigh_scattering I'm not sure how any of that is relevant to refraction or the fact that photons always move at c. Link to comment Share on other sites More sharing options...
Itoero Posted October 21, 2017 Author Share Posted October 21, 2017 On 10-10-2017 at 4:20 PM, Strange said: I'm not sure how any of that is relevant to refraction or the fact that photons always move at c. It's all about the energy of a photon. We observe different colors due to a change in photon energy. The amount of energy is directly related to the photon's electromagnetic wavelength and frequency. Link to comment Share on other sites More sharing options...
swansont Posted October 21, 2017 Share Posted October 21, 2017 1 hour ago, Itoero said: It's all about the energy of a photon. We observe different colors due to a change in photon energy. The amount of energy is directly related to the photon's electromagnetic wavelength and frequency. Which has nothing to do with what Strange observed. Link to comment Share on other sites More sharing options...
Itoero Posted October 21, 2017 Author Share Posted October 21, 2017 1 hour ago, swansont said: Which has nothing to do with what Strange observed. This is what Strange said: "refraction is due to the interaction of the photons with electrons but they continue to move at c. " The Compton and Rayleigh scattering is about the interacting of photons with electrons (or atoms or molecules) which cause refraction. I don't get how that's irrelevant. It's also a direct reply on my own question in the OP. Link to comment Share on other sites More sharing options...
Strange Posted October 21, 2017 Share Posted October 21, 2017 Scattering is not refraction. Link to comment Share on other sites More sharing options...
Itoero Posted October 21, 2017 Author Share Posted October 21, 2017 15 minutes ago, Strange said: Scattering is not refraction. Refraction is a form of scattering. Link to comment Share on other sites More sharing options...
Strange Posted October 21, 2017 Share Posted October 21, 2017 24 minutes ago, Itoero said: Refraction is a form of scattering. Errr..... How shall I put this ... No. Link to comment Share on other sites More sharing options...
Itoero Posted October 22, 2017 Author Share Posted October 22, 2017 18 hours ago, Strange said: Errr..... How shall I put this ... No. Refraction occurs because of scattering. Refraction occurs when a large number of particles(dipoles) scatter coherently. Link to comment Share on other sites More sharing options...
dimreepr Posted October 22, 2017 Share Posted October 22, 2017 6 minutes ago, Itoero said: Refraction occurs because of scattering. Refraction occurs when a large number of particles(dipoles) scatter coherently. https://en.wikipedia.org/wiki/Refraction https://en.wikipedia.org/wiki/Dipole You need to do some reading... LOL, what a surprise a neg rep from It... 3 Link to comment Share on other sites More sharing options...
Itoero Posted October 22, 2017 Author Share Posted October 22, 2017 (edited) Let's simple it down. Refraction is the change in direction of wave propagation due to a change in its transmission medium. The photons ( or whatever the wave is made of) interact with the particles of the new medium which causes a different scattering, which bends the wave. Edited October 22, 2017 by Itoero Link to comment Share on other sites More sharing options...
Strange Posted October 22, 2017 Share Posted October 22, 2017 6 hours ago, Itoero said: Refraction is the change in direction of wave propagation due to a change in its transmission medium. The photons ( or whatever the wave is made of) interact with the particles of the new medium which causes a different scattering, which bends the wave. It is NOT scattering. This page https://en.wikipedia.org/wiki/Scattering does not include the word "refraction." This page https://en.wikipedia.org/wiki/Refraction does not include the word "scattering." Do you know why that is? Can you guess? It is a bit immature to give people a down vote just for pointing out that you are wrong. Link to comment Share on other sites More sharing options...
swansont Posted October 23, 2017 Share Posted October 23, 2017 Refraction is a classical phenomenon that can be explained without invoking scattering from QM interactions. Link to comment Share on other sites More sharing options...
Itoero Posted October 23, 2017 Author Share Posted October 23, 2017 15 hours ago, Strange said: It is NOT scattering. This page https://en.wikipedia.org/wiki/Scattering does not include the word "refraction." This page https://en.wikipedia.org/wiki/Refraction does not include the word "scattering." Do you know why that is? Can you guess? It is a bit immature to give people a down vote just for pointing out that you are wrong. You read but you don't understand and that's not why I gave him a down vote. Refraction is about bending of wave propagation due to a change in transmission medium. A wave and transmission medium exist out of particles unless the medium is a vacuum...then it depends how you define a particle. A wave cannot change course without scattering of its particles. Unless light travels trough vacuum, the photons scatter. This is what Rayleigh and Compton scattering are about. Rayleigh scattering is an important component of the scattering of optical signals in optical fibers. Silica fibers are glasses, disordered materials with microscopic variations of density and refractive index. In the formula, you calculate the scattering with the refractive index. https://en.wikipedia.org/wiki/Rayleigh_scattering In detail, the intensity I of light scattered by any one of the small spheres of diameter d and refractive index n from a beam of unpolarized light of wavelength λ and intensity I0 is given by...(see link) It's all about wave particle duality. The bending of wave propagation is due to the interacting of its particles. 11 hours ago, swansont said: Refraction is a classical phenomenon that can be explained without invoking scattering from QM interactions. That's true, if you don't like wave particle duality... Link to comment Share on other sites More sharing options...
Strange Posted October 23, 2017 Share Posted October 23, 2017 4 minutes ago, Itoero said: Refraction is about bending of wave propagation due to a change in transmission medium. Yes. That allows us to make thing like lenses. A lens that scattered light (because the surface was matt or it was full of impurities) would not be very useful. 5 minutes ago, Itoero said: A wave and transmission medium exist out of particles Irrelevant to refraction, which can be explained with classical waves and the bulk properties of materials. The scattering of light by particles, obviously depends on the particles. But, again, can be explained in terms of classical waves. Quote A wave cannot change course without scattering of its particles. 1. A wave can. A wave isn't made of particles. 2. Scattering is not the cause of refraction. Scattering causes light to be scattered in multiple directions (the clue is in the name). If you have frosted glass in a window, that will scatter light and any refraction by the glass will probably be undetectable. 8 minutes ago, Itoero said: you calculate the scattering with the refractive index Yes, because that defines how the light interacts with the particle. So, yes, scattering is affected by refractive index. But refraction is not scattering. 9 minutes ago, Itoero said: It's all about wave particle duality. Not really. It can be explained classically. 9 minutes ago, Itoero said: The bending of wave propagation is due to the interacting of its particles. Yes. It can be described that way. So can scattering. And reflection. And absorption. That doesn't mean they are all the same thing. Link to comment Share on other sites More sharing options...
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