Jacques Posted September 1, 2005 Share Posted September 1, 2005 Hi I readed in many threads in this forum that the speed of light is constant even in a meium like water or glass. That the apparent slowing down is cause by the photons being absorbed by the atoms of the medium and after a moment being re-emitted. The speed of the photon between atom is always c. My question is Why doesn't the light is scattered, dispersed ? How does the atom remember from which direction the photon came ? Thanks For your answers Link to comment Share on other sites More sharing options...
Xyph Posted September 1, 2005 Share Posted September 1, 2005 The atom doesn't remember anything. If a photon hits a nucleus it will be deflected or absorbed, and if this happens a lot I assume the light will be scattered and dispersed. Just remember that atoms are mostly empty space though, so there's plenty of room for the photons to move in without hitting anything. Link to comment Share on other sites More sharing options...
5614 Posted September 1, 2005 Share Posted September 1, 2005 And then how does a molecule know always to reflect so that i=r ??? I've always wondered this and the original question. Link to comment Share on other sites More sharing options...
CPL.Luke Posted September 1, 2005 Share Posted September 1, 2005 why does the E field remember to get weaker at the rate of 1/r^2 ? Link to comment Share on other sites More sharing options...
Jacques Posted September 1, 2005 Author Share Posted September 1, 2005 so there's plenty of room for the photons to move in without hitting anything I know. How do you explain the change in speed of the light in a medium ? I was refering to some explainations given to that in this forum. Link to comment Share on other sites More sharing options...
5614 Posted September 1, 2005 Share Posted September 1, 2005 How do you explain the change in speed of the light in a medium ? Because photons are continuously absorbed and reemitted, this processes take time, we're still talking tiny amounts of time, but when referring to light a small time makes a noteable difference. Link to comment Share on other sites More sharing options...
Jacques Posted September 1, 2005 Author Share Posted September 1, 2005 Because photons are continuously absorbed and reemitted, Then why doesn't the photons scattered ? If a photon is absorbed by an atom it can be reemitted in any direction, not necessarily in the same direction. Link to comment Share on other sites More sharing options...
J.C.MacSwell Posted September 1, 2005 Share Posted September 1, 2005 I always pictured light staying at "c" but having further to travel (around molecules) in different mediums, but also have been puzzled by this "absorbtion/readmission". Do photons have a much greater likelyhood of being readmitted in the same direction they were going (prior to absorbtion) in transparent materials? Link to comment Share on other sites More sharing options...
swansont Posted September 2, 2005 Share Posted September 2, 2005 Then why doesn't the photons scattered ? If a photon is absorbed by an atom it can be reemitted in any direction, not necessarily in the same direction. AFAIK it's because the absorption is in virtual states, and conservation of momentum requires them to be reemitted in the same direction. Scattering happens when the interaction is with a real state. Link to comment Share on other sites More sharing options...
5614 Posted September 3, 2005 Share Posted September 3, 2005 What do you mean by a virtual state and a real state? Link to comment Share on other sites More sharing options...
x__heavenly__x Posted September 3, 2005 Share Posted September 3, 2005 Well, This absorbtion and reemision is just an analogy, in reality photons , which r just vibrational energy(not at all particles, like in the real sence) just hit go through a medium and get deflected, just as they enter a medium, u know refraction happens at the surface. Ok as it hits the surface, they get an effect of being thrown out of their original path. and in the medium continue in that deflected path, when they exit, they get deflected in the same way but reverse....so original path again.... But there was something which always bothered me...light will get diflected only to the plane its traveling....like a line of laser in a 2d plane, traveling at x+y will get diflected in the x-y plane not the z plane, even though in 3d world...i donno wat happens. Link to comment Share on other sites More sharing options...
swansont Posted September 3, 2005 Share Posted September 3, 2005 What do you mean by a virtual state and a real state? A real state is one of the quantized energy states you would get if you could solve the Schroedinger equation for that atom in question, e.g. the 10.2 eV for the first excited state in Hydrogen. Monochromatic light, far from any absorption line, still sees an index n>1 when passing through a vapor. The photons are not absorbed in a transition that puts the electron in an allowed state, so this can only happen for a short time. Consequently, the photon can't transfer momentum to the atom and has to be re-emitted in the same direction. (Heisenberg Uncertainty Principle) Classically it's just the interactions with the fields in place that change the permittivity and permeability, slowing the wave down. Link to comment Share on other sites More sharing options...
GeminiinimeG Posted September 6, 2005 Share Posted September 6, 2005 I have no idea what I am typing but here it goes, the gravity within the atoms affects the light? or maybe the light is being slowed down by all the atoms in its way, how does this work???? Maybe the photons bounce around within the water and seems that the ones that make it thought to the other side will be dimmer and weill seem to be slowed but its just many of them were absorved or they bounced off somewere else. am i correct Link to comment Share on other sites More sharing options...
5614 Posted September 6, 2005 Share Posted September 6, 2005 I have no idea what I am typing That is correct. am i correct No. how does this work???? Try reading the thread, even the original poster stated it! btw, gravity has not been observed on a subatomic level, it is too weak as a force. Link to comment Share on other sites More sharing options...
x__heavenly__x Posted September 7, 2005 Share Posted September 7, 2005 A have to agree with 5614. Am i evil? Link to comment Share on other sites More sharing options...
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