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While reading up on Cerenkov radiation, the first question that came to mind was "Why would light travel slower in a higher density medium (water) ?" I found the following explanation :
At source : http://www.madsci.org/posts/archives/1998-05/893732585.Ph.r.html"
Is this correct ? I know that the vast majority of photon absorption-emission events result in an emitted photon with a longer wavelength than the absorbed one - and within the emission band-widths of the absorbing molecule. What exactly is the difference between the 2 absorption types described here (the none wavelength-shifting, and the wavelength-shifting) ?
Another thing is - in any energetic interaction, all the participants "get something" for their trouble, if a molecule absorbs and emits the same wavelength of photon, what does the molecule get out of this "deal" ? (I also think that theoretically, the wavelength of the photon can not be exactly the same, the laws of thermodynamics ensure some losses).
Can the Cerenkov radiation be compared to aurora boralis, or any other photonic emission resulting from charged particles traveling through a magnetic field ?
And finally : As far as we know at this stage, the speed of light is an absolute and a limit within any local reference frame. When a photon looses energy, the energy loss expresses itself in a wavelength shift, not a lower speed. So if the explanation given above for the lower speed of light in water is not correct - what is ? I can not imagine anything other than higher dimensions causing this...
Another of your statements is "Light will slow down when entering an
optically dense medium." Actually this is not quite true. While it
is true that we measure a lower AVERAGE speed of the light through a
medium, the propagation of light through the medium, between atoms, is
actually at the normal vacuum speed of light, c. What happens is that
the light moves at speed c between atoms, but photons are "absorbed"
by the atoms. By "absorption" I mean that the energy of the
photon causes an electron of the atom to be kicked to a higher energy
level, and the photon ceases to exist. Then, after a very small time
delay, the electron goes back to its original (usually ground state)
energy and "emits" a photon of the same energy (and thus same
frequency and thus same wavelength) as the original "absorbed" photon.
(In fluorescent materials the energy of the photon is downshifted, but
I am talking here of "elastic", or non-energy shifting, absorptions.)
It is this very small time delay which makes us measure the average
"speed of light" through the medium as slower than the vacuum speed of
light. But, again, between atoms the light does travel at the speed
c.
At source : http://www.madsci.org/posts/archives/1998-05/893732585.Ph.r.html"
Is this correct ? I know that the vast majority of photon absorption-emission events result in an emitted photon with a longer wavelength than the absorbed one - and within the emission band-widths of the absorbing molecule. What exactly is the difference between the 2 absorption types described here (the none wavelength-shifting, and the wavelength-shifting) ?
Another thing is - in any energetic interaction, all the participants "get something" for their trouble, if a molecule absorbs and emits the same wavelength of photon, what does the molecule get out of this "deal" ? (I also think that theoretically, the wavelength of the photon can not be exactly the same, the laws of thermodynamics ensure some losses).
Can the Cerenkov radiation be compared to aurora boralis, or any other photonic emission resulting from charged particles traveling through a magnetic field ?
And finally : As far as we know at this stage, the speed of light is an absolute and a limit within any local reference frame. When a photon looses energy, the energy loss expresses itself in a wavelength shift, not a lower speed. So if the explanation given above for the lower speed of light in water is not correct - what is ? I can not imagine anything other than higher dimensions causing this...
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