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I thought that showing Einstein was wrong would be a big deal.

Relativity does not address the quantum scale, although his work on the photoelectric effect does.

Re the speed of light in general - I have asked elsewhere on this forum about the scientist who has slowed down light and even stopped it at one point, and why this is not being celebrated/discussed/questioned/debated/explored more. Is this scientist's discovery (Lene Haus) not that important after all? I thought that showing Einstein was wrong would be a big deal.

So, as (light) slows down, the energy gets higher

There is a relativistic theory of quantum mechanics.

How does light speed up when it exits a denser material?

Light which exits the material it's not the same light which enters and which is inside: the em field which exits is generated by the last charges inside the material.

Quote from: LightarrowLight which exits the material it's not the same light which enters and which is inside: the em field which exits is generated by the last charges inside the material.Explanations often say, or imply, that it is not a single photon that travels through the medium (e.g. glass); it is a succession of new photons, created at each new emission from atoms in the glass. If this were what actually happened, then the absorption spectrum would be discrete because atoms have only discrete energy states. Yet, in glass for example, we see almost the whole visible spectrum being transmitted with no discrete disruption in the measured frequencies.The reason for this is that a solid is composed of a network of ions and electrons fixed in a "lattice". They have what is known as "collective vibrational modes", or phonons. These are quanta of lattice vibrations, and it is these vibrational modes that can absorb a photon. If a photon has an energy beyond the phonon spectrum, the solid cannot sustain this vibration, because the phonon mode is not available; so the lattice does not absorb this photon and it is re-emitted but with a very slight delay.

Infact I haven't written that a photon is absorbed by an atom's material then ri-emitted and so on.

And interestingly, if an infra-red photon passed through the translucent material would it be visible on its passage as ‘red light’?

No, the frequency determines the "color," and that does not change from medium to medium. The wavelength must change, but ultimately it is the frequency (energy) that registers as the color in our eye.If you consider the eye as the detector, then it doesn't matter what material the light passes through, ultimately the refractive index of the eye where the light is absorbed determines the "observed wavelength", but we can design an experiment to probe the color of light in other materials:Say we have two solutions that each contain the same concentration of a dye that absorbs at a very specific frequency, but the two solutions also contain different amounts of some other dissolved species that changes the refractive index substantially (many additives could allow us to tune the refractive index by 10-20%, without changing the behavior of the dye). If the spectrum of light coming out of the solution is independent of the refractive index, that proves that the frequency determines color, not the wavelength (and if the absorbed light shifts with refractive index, that proves the wavelength is the important factor)

I disagree. The explanation that the reduction of the velocity of visible light in a translucent material is effected by a reduction in wavelength but not frequency, implies that the sinusoidal wave model of a single photon is incorrect. With the sinusoidal model, the wavelength and frequency are related, one being the inverse of the other.

The only way I can see to explain the reduction of light speed upon entering a translucent material from say, air, is if the amplitude of the sinusoidal wave is increased at the boundary between the media, but its frequency and wavelength remain unchanged. The higher amplitude increases the three dimensional distance travelled by the photon's new sinusoidal wave form and hence its velocity through the medium. On emerging from the translucent medium back into air, the amplitude reverts to its previous level, giving the photon the energy it needs to return to its previous velocity.

Reading the results of experimental tests upon the functioning of the eye, their results all refer to the wavelength of the visible light as being the important factor in the colours that the brain observes, not frequency.

Absorption and refraction are two different phenomenon, not to be confused. Refraction or bending of light occurs at the surface boundary between the two media. Absorption of a particular frequency of light by electrons can happen anywhere within the receiving medium. In the experiment you described, adding the dye to the change of refractive index would only shift the whole light spectrum to one side. The absorption frequency of the translucent solution would be unchanged within this spectrum, proving nothing. Except that the added dye does not absorb light of the particular frequency used in the experiment. I'm assuming that the absorption line did not move!

I disagree. The explanation that the reduction of the velocity of visible light in a translucent

material is effected by a reduction in wavelength but not frequency, implies that the sinusoidal wave model of a single photon is incorrect

. With the sinusoidal model, the wavelength and frequency are related, one being the inverse of the other.

The only way I can see to explain the reduction of light speed upon entering a translucent material from say, air, is ...

The wavelength changes based on the refractive index of the medium the light is in (see above), but the frequency (energy) remains constant

a photon entering the material is not the same photon exiting from it: the em field, entering the material, let's say glass, excites it and the glass generates in turn another em field, which interacts with the first and with glass itself. Photons are constantly created and destroyed in the resulting field so their individuality is lost at the end of the path.

Presuming light has a speed

Presuming light ...is not something in space that is being energized at a speed such as CBMR.

Quote from: Lightarrowa photon entering the material is not the same photon exiting from it: the em field, entering the material, let's say glass, excites it and the glass generates in turn another em field, which interacts with the first and with glass itself. Photons are constantly created and destroyed in the resulting field so their individuality is lost at the end of the path.Maybe I'm just nitpicking here, but...I would call a photon an em field which propagates through space, as per Maxwell's equations.

To me, it doesn't matter whether the em field at point X is the same em field that exists 1 meter (or 1 micrometer) away. What matters is that it is the same quantum of energy that is propagating (as per Einstein's explanation of the photoelectric effect).

To me, the photon that enters a glass block is the same photon that exits a glass block (assuming it isn't absorbed in-between).

Then an electron or a photon is the same, for you

Prove it, if you can.

QuoteThen an electron or a photon is the same, for youNo, an electron does not obey Maxwell's equations (in particular, it cannot travel at c); a photon does.

QuoteProve it, if you can.I don't think it is a matter of proof. I think it comes down to how it is defined.

I don't know what would be an authoritative definition, but in ...sorry, you cannot view external links. To see them, please REGISTER or LOGIN--lightarrow

QuoteProve it, if you can.I don't think it is a matter of proof. I think it comes down to how it is defined.I don't know what would be an authoritative definition, but in ...sorry, you cannot view external links. To see them, please REGISTER or LOGINQuote ..the focus is on the photon as a quantum of energy, rather than on the photon as a localized disturbance in the em field.More authoritative definitions & interpretations are welcome!It's very difficult to find one because it's a very technical subject, despite the fact we always talk about it as if we knew it well...Here is one from an extract of a discussion in other forum (and I admit not to have completely grasped it []):Given a free electromagnetic field (that is without electric charges) a photon is (something alike) the subspace with n = 1 of the hilbert space of quantized field's states, where n are eigenvalues of the operators "number of particles" N which gives the hamiltonian of the field when multiplied by ħω, which gives the field energy when applied to the state.--lightarrow

..the focus is on the photon as a quantum of energy, rather than on the photon as a localized disturbance in the em field.More authoritative definitions & interpretations are welcome!

You are mixing classical and quantum concepts here. If you want to talk of Maxwell's equations, then forget the word "photon".

I'm about to start reading up on Hilbert spaces.

When you calculate the path and speed of a photon through a block of glass, you must do a calculation at the boundaries of the glass block, because the conditions change (ie glass has a higher refractive index than air), and this affects the speed of the photon. It does not matter whether you are using classical optics or ...sorry, you cannot view external links. To see them, please REGISTER or LOGIN to do the calculation.

QuoteYou are mixing classical and quantum concepts here. If you want to talk of Maxwell's equations, then forget the word "photon".The fact that QED is able to unify the behaviour of photons & electrons makes it better than classical physics; maybe one day we will have a theory that includes gravity too, and that will be even better than QED.But the existence of a "better" theory does not necessarily render the old theory invalid.

The new theory is only considered valid because in the "classical limit", it predicts the same results as the experiments which had already been successfully explained by the classical theory. So in selecting a method to solve a particular problem, it is important to know how accurate an answer do you need? All design calculations are approximations; will the approximations of a given method yield an answer which is "good enough" for the problem at hand? This means you must understand the domain of applicability of the different theories:Where they will give essentially identical answersWhere they will give answers that are "close enough", and you can build a prototype and tweak it to correct the discrepancies that occur because real objects are never exactly the same as even the best theoretical models.Where they give divergent answers, and you must use the more complex theory (but you still need to build the prototype!). In cases 1 & 2, the selection is essentially made on pragmatic grounds like simplicity and accuracy (the proverbial "back of the envelope calculation" may be all you can afford in the middle of a discussion).

For myself, my maths classes did not go beyond eigenvectors on finite dimensional vector spaces, so I don't have all the mathematical tools needed for determining the eigenvalues of infinite-dimensional Hilbert spaces. However, I would argue that you do not need these advanced mathematical tools to calculate the path and speed of a photon through a glass block, because this is in the domain of classical optics. The answers are "close enough", provided the size of the block of glass is much larger than the wavelength of light, and the size of the atoms in the glass is far smaller than the wavelength of the light. You just need to recognize that the classical term "a ray of light" is an approximation to "a stream of photons" in quantum theory.

Undoubtedly, a grand unified theory which includes gravity (or even a small extension of current theories which is able to explain why calculations on Feynman diagrams work so well) will require additional, even more complex mathematical tools in your toolkit. You don't always need a sledgehammer to crack a nut...

I have never read anywhere that wave amplitude is a factor. Do you have any references for that?

if it is a fact that the wavelength of a photon changes, then how does this actually happen?

rebut the logic of an amplitude variation in the photon

Quote from: jeffreyH on 27/07/2015 17:16:02I'm about to start reading up on Hilbert spaces.Good. Let me know what you grasped (or not).--lightarrow

as a photon enters a block of glass causes a proportional reduction in wavelength inside the glass.

Quote as a photon enters a block of glass causes a proportional reduction in wavelength inside the glass.Surely you mean a proportionate increase in wave - length ?

At the moment I am reading through quantum physics. I now understand the double slit experiment and the relationship between photon wave length and measurement. Also exactly why position and momentum cannot be measured together. I have started on complex vector spaces and bra ket notation and am up to complex conjugates. When I get further I may have questions.

IF the quantum world experiences time at a rate much slower to our own experience, Planck's h constant would actually be 'blocking' the view of quantum activity.The implications of this notion are that the quantum world may not be granular but may in fact be as smooth as the macroscopic world, and if Planck's h constant were to be variable in accordance to the variability of the length/rate of a second... then perhaps it would be possible to measure both location and velocity simultaneously.

Poppycock.

Quote from: timey on 04/08/2015 12:37:10IF the quantum world experiences time at a rate much slower to our own experience, Planck's h constant would actually be 'blocking' the view of quantum activity.The implications of this notion are that the quantum world may not be granular but may in fact be as smooth as the macroscopic world, and if Planck's h constant were to be variable in accordance to the variability of the length/rate of a second... then perhaps it would be possible to measure both location and velocity simultaneously.Poppycock.

It has been mentioned above as to an exchange of energies between the light and the medium it is passing through affecting frequency.IF... (I have my ideas, but I'll say 'for whatever reason')... If the length/rate of a second is not a constant then Planck's h constant can actually be considered as a variable. If velocity is measured by seconds that are not constant then the length measurement is affected.

We know that mass and a gravity field affect the phenomenon of time dilation...

IF we can view the experience of time from the perspective of the quantum world as being of a different length/rate of second in relation to our own experience of time, then Planck's h constant becomes an inadequate tool in the measurement of lengths/frequencies.

IF the quantum world experiences time at a rate much slower to our own experience, Planck's h constant would actually be 'blocking' the view of quantum activity.The implications of this notion are that the quantum world may not be granular but may in fact be as smooth as the macroscopic world, and if Planck's h constant were to be variable in accordance to the variability of the length/rate of a second... then perhaps it would be possible to measure both location and velocity simultaneously.Under the remit of this notion, the energies exchanged between the light and the medium of the glass would be time related.

Nope, I'm not confusing these relativity/space time related considerations of proper time or co-ordinate time. I do have my own ideas on time - but this thread is not my thread, nor is it in the new theories section...therefore for the purposes of this conversation I think it within the remit of accepted physics to say that we have time as a measurement and, as a separate issue, that we observe the occurrence of the phenomenon of time... and that this time is subject to change in the rate of its occurrence due to changes in the gravity field.Of course my post/posts are entirely speculative, , is there something wrong with that?IF we can view gravity fields on a smaller scale, as in our own personal gravity field, ie: if we get fatter we feel heavier, if we go to the moon we feel lighter... on the basis that a black hole will change the rate of time fairly drastically, 'maybe' the gravity fields of the quantum world are 'differently oriented' in relation to to time dilation.The smallest quantum package is delivered at an unbelievably small fraction of a 'second'. Clearly Planck has used a time measurement factor in the derivation of this constant... But IF the quantum world is operating within a time structure that is different, ie not occurring at the same rate as our own, the time measurement that Planck has used to derive these units of Planck time as constant would be rendered inadequate in measuring the entirety of the quantum world. The gaps between the quantum leaps being the point of relevance here.