Mellinia Posted August 31, 2012 Share Posted August 31, 2012 Why doesn't the frequency of light change after it is perfectly refracted? Is it because of the conservation of energy? Link to comment Share on other sites More sharing options...
Harish Srinivasan Posted September 7, 2012 Share Posted September 7, 2012 It is with the principle of Least action that the law of refraction works - which implies that light has to minimize the time taken to travel in the medium. To my knowledge I think this effectively done by altering the wavelength rather than frequency since the frequency of light would have to be the inverse of time taken for light to travel a distance of wavelength. About the conservation of energy I am not sure, the conservation of energy (E = hv) - its not just v(freq) can remain constant; it can also be given by E=hc/λ but since c changes the value of λ also has to change to keep E constant. But again you might have to reason why c changes. Link to comment Share on other sites More sharing options...
Mellinia Posted September 7, 2012 Author Share Posted September 7, 2012 It is with the principle of Least action that the law of refraction works - which implies that light has to minimize the time taken to travel in the medium. To my knowledge I think this effectively done by altering the wavelength rather than frequency since the frequency of light would have to be the inverse of time taken for light to travel a distance of wavelength. About the conservation of energy I am not sure, the conservation of energy (E = hv) - its not just v(freq) can remain constant; it can also be given by E=hc/λ but since c changes the value of λ also has to change to keep E constant. But again you might have to reason why c changes. Well, c is always constant(the speed of light?!) but I have no idea as to why wavelength is altered but frequency is not. Link to comment Share on other sites More sharing options...
Joatmon Posted September 7, 2012 Share Posted September 7, 2012 You might like to follow the link which states the speed of light in the medium is different to the speed of light in a vacuum. Not really my field, but seems interesting. http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/refr.html Link to comment Share on other sites More sharing options...
Mellinia Posted September 7, 2012 Author Share Posted September 7, 2012 You might like to follow the link which states the speed of light in the medium is different to the speed of light in a vacuum. Not really my field, but seems interesting. http://hyperphysics....eoopt/refr.html yeah, but the speed of photons remain the same, right? Do photons lose energy when they pass through something transparent? Link to comment Share on other sites More sharing options...
swansont Posted September 7, 2012 Share Posted September 7, 2012 yeah, but the speed of photons remain the same, right? Do photons lose energy when they pass through something transparent? The speed of transmission decreases in a medium, v = c/n, though the photon speed is always c (photons are absorbed and re-emitted from virtual states, which delays the overall time). The energy remains the same. Link to comment Share on other sites More sharing options...
Mellinia Posted September 7, 2012 Author Share Posted September 7, 2012 The speed of transmission decreases in a medium, v = c/n, though the photon speed is always c (photons are absorbed and re-emitted from virtual states, which delays the overall time). The energy remains the same. So, the frequency remains the same but wavelength changes because the energy of photons are constant and wavelength is not related to its energy? Link to comment Share on other sites More sharing options...
swansont Posted September 7, 2012 Share Posted September 7, 2012 So, the frequency remains the same but wavelength changes because the energy of photons are constant and wavelength is not related to its energy? The wavelength is related to the energy but the relationship also scales with n, so the energy is unchanged. Link to comment Share on other sites More sharing options...
Mellinia Posted September 7, 2012 Author Share Posted September 7, 2012 The wavelength is related to the energy but the relationship also scales with n, so the energy is unchanged. n being the refractive index? Link to comment Share on other sites More sharing options...
swansont Posted September 7, 2012 Share Posted September 7, 2012 n being the refractive index? Yes. Link to comment Share on other sites More sharing options...
Ronald Hyde Posted September 8, 2012 Share Posted September 8, 2012 Well, c is always constant(the speed of light?!) but I have no idea as to why wavelength is altered but frequency is not. Yes, C is a constant of Nature all the time, but in the piece of glass the photons don't travel at C, they travel at a speed determined by the Index of Refraction of the glass, which is closely related to its Dielectric Constant. Link to comment Share on other sites More sharing options...
swansont Posted September 8, 2012 Share Posted September 8, 2012 Yes, C is a constant of Nature all the time, but in the piece of glass the photons don't travel at C, they travel at a speed determined by the Index of Refraction of the glass, which is closely related to its Dielectric Constant. The light doesn't travel at c, but the photons do. Link to comment Share on other sites More sharing options...
abvegto Posted September 9, 2012 Share Posted September 9, 2012 yes....it is in accord with law of conservation of energy.......when light enters any medium its electric field interacts with those of the electrons of the medium and hence the electric field is disturbed .....and hence the speed "appears" to have been altered w.r.t our frame... but in that frame of reference( i.e w.r.t the medium itself )... light still travels at c... Link to comment Share on other sites More sharing options...
O'Nero Samuel Posted September 10, 2012 Share Posted September 10, 2012 The light doesn't travel at c, but the photons do. That is to say that in vacuum, photons travels at c (the speed of light), but through a medium, photons are transmitted at a speed, v=c/n, relative to our frame of reference. Link to comment Share on other sites More sharing options...
swansont Posted September 10, 2012 Share Posted September 10, 2012 That is to say that in vacuum, photons travels at c (the speed of light), but through a medium, photons are transmitted at a speed, v=c/n, relative to our frame of reference. In a medium, the photons travel at c, while the overall transit speed is c/n. There is a delay for absorbing/emitting photons that accounts for the longer transit time. IOW, photons travel at c, while light travels at c/n. Link to comment Share on other sites More sharing options...
O'Nero Samuel Posted September 10, 2012 Share Posted September 10, 2012 Is n permitivity of the transmitting space/medium, refractive index or some sorte of "dielectric" constant that determine the speed at which light travels? Link to comment Share on other sites More sharing options...
swansont Posted September 11, 2012 Share Posted September 11, 2012 Is n permitivity of the transmitting space/medium, refractive index or some sorte of "dielectric" constant that determine the speed at which light travels? Yes. Link to comment Share on other sites More sharing options...
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