Strange Posted September 13, 2015 Share Posted September 13, 2015 If I used a prism and then an inverted prism what would happen to the photons? This was part of the experiment that Newton did to demonstrate that white light is made up of a number of colours (7 in his imagination, an infinite number in reality) Link to comment Share on other sites More sharing options...
John Cuthber Posted September 13, 2015 Share Posted September 13, 2015 This was part of the experiment that Newton did to demonstrate that white light is made up of a number of colours (7 in his imagination, an infinite number in reality) It is worth noting that it was a very important experiment. The view had been that the prism somehow "added" colours to the white light. Sending it through a second prism and having it turn white again disproved that idea. Link to comment Share on other sites More sharing options...
Asimov Posted September 14, 2015 Share Posted September 14, 2015 Patushkagoogol; Entanglement doesnt apply. Try this perspective. Photons have wavelength but no color.We and our ancestors invented color. Helps find the ripe fruit and mates, game and predators..Color is how we percieve photons of various wavelength. Right, color is all in our head. The cones are receptors in the eye that fire in response to a particular wavelength photon. There are only three type cones. One for red, one for blue and one for green. How they collectively fire determins the color we percieve. When all three fire we call this white light. Why and how white? Again our visual system made this up. All the other colors like yellow are just how we interpret combinations of wavelengths.Our visual system is quite a computer enhancer. The eye is a terrible camera. The image on the retina is upside down and badly destorted with many blind areas that our brain enhances and fills in.. We are successful because this system gives us pretty accurate overall input of our environment. 1 Link to comment Share on other sites More sharing options...
petrushka.googol Posted September 14, 2015 Author Share Posted September 14, 2015 As a corollary, how does dispersion actually happen ? Photons are split by frequency (which is why we get the notion of colors. What I am trying to suggest is that there is some sort of internal coupling or harmonization that takes place (based on different frequencies), which can be sampled when dispersion takes place. PS maybe entanglement is the wrong word. Link to comment Share on other sites More sharing options...
Strange Posted September 14, 2015 Share Posted September 14, 2015 As a corollary, how does dispersion actually happen ? Photons are split by frequency (which is why we get the notion of colors. What I am trying to suggest is that there is some sort of internal coupling or harmonization that takes place (based on different frequencies), which can be sampled when dispersion takes place. Do you have any evidence for this "coupling"? What effect does it have, that is not explained by current theory? Link to comment Share on other sites More sharing options...
petrushka.googol Posted September 14, 2015 Author Share Posted September 14, 2015 Do you have any evidence for this "coupling"? What effect does it have, that is not explained by current theory? Having photons of excited to different frequencies maintaining their inherent state and relationship and always combining to give the notion of white light seems to be more than random coincidence. If any group of photons loses energy then the continuous spectrum will be broken. Link to comment Share on other sites More sharing options...
Strange Posted September 14, 2015 Share Posted September 14, 2015 Having photons of excited to different frequencies maintaining their inherent state and relationship and always combining to give the notion of white light seems to be more than random coincidence. If any group of photons loses energy then the continuous spectrum will be broken. Why would photons lose energy? A photon of a given energy will always have that energy. (Apart from things like Doppler effect or gravitational red-shift, which could change the colour from white.) If you reflect white light off some surfaces then photons with particular energies might be absorbed and others reflected. The result is light that is not white. Link to comment Share on other sites More sharing options...
swansont Posted September 14, 2015 Share Posted September 14, 2015 Having photons of excited to different frequencies maintaining their inherent state and relationship and always combining to give the notion of white light seems to be more than random coincidence. If any group of photons loses energy then the continuous spectrum will be broken. But they do maintain their state, unless they interact with something. They generally don't interact with each other (unless you have high energies and intensities, IIRC) So there's nothing to make them lose energy as they travel through space. Link to comment Share on other sites More sharing options...
Asimov Posted September 14, 2015 Share Posted September 14, 2015 Patrushka.googol:Are you looking for some property of light other than frequency that causes us to percieve different colors? You may be headed in the wrong direction.The property of light that determins the color we percieve is frequency. At least that is what I learned over 1/2 century ago. White light is what we call the mixture of frequencies in white light. Thats all. Color is entirely subjective. Here is a little more detail regarding the specialized cone receptors.We have color vision because of 3 cones with different opsins that each have peak absorption for different frequencies. Red, 620- 750 nm etc.. The retina itself is able to selectively amplify or inhibit the respective cone signals by means of cross conections..Brain cells further modulate the signals. Entanglement doesnt seem to be involved as far as I know. Link to comment Share on other sites More sharing options...
swansont Posted September 14, 2015 Share Posted September 14, 2015 Also, as the perception of light is a biological question at least as much as it is a physics one, some aspects of the issue may have nothing to do with physics. 1 Link to comment Share on other sites More sharing options...
Klaynos Posted September 14, 2015 Share Posted September 14, 2015 Also, as the perception of light is a biological question at least as much as it is a physics one, some aspects of the issue may have nothing to do with physics. This is why I asked my still unanswered question about what he means by colour. I think including what he means by white light is also probably relevant at this point. Link to comment Share on other sites More sharing options...
studiot Posted September 14, 2015 Share Posted September 14, 2015 Patushkagoogol; Entanglement doesnt apply. Try this perspective. Photons have wavelength but no color.We and our ancestors invented color. Helps find the ripe fruit and mates, game and predators..Color is how we percieve photons of various wavelength. Right, color is all in our head. The cones are receptors in the eye that fire in response to a particular wavelength photon. There are only three type cones. One for red, one for blue and one for green. How they collectively fire determins the color we percieve. When all three fire we call this white light. Why and how white? Again our visual system made this up. All the other colors like yellow are just how we interpret combinations of wavelengths.Our visual system is quite a computer enhancer. The eye is a terrible camera. The image on the retina is upside down and badly destorted with many blind areas that our brain enhances and fills in.. We are successful because this system gives us pretty accurate overall input of our environment. This is the best post I've seen you make. +1 for encouragement. Link to comment Share on other sites More sharing options...
petrushka.googol Posted September 15, 2015 Author Share Posted September 15, 2015 This is why I asked my still unanswered question about what he means by colour. I think including what he means by white light is also probably relevant at this point. color = frequency. white light = mixture of frequencies. Why is it that the mixture is always perfect ? (All colors combine to get the notion of white.). My poser is "Why is the perception always the same?" (give or take a few photons....). Link to comment Share on other sites More sharing options...
Asimov Posted September 15, 2015 Share Posted September 15, 2015 Petrushkagoogol: G Link to comment Share on other sites More sharing options...
Strange Posted September 15, 2015 Share Posted September 15, 2015 Why is it that the mixture is always perfect ? (All colors combine to get the notion of white.). What do you mean by "always perfect"? Not all light is white (or perfect). Not all white light remains white (if it passes through or bounces of a coloured material, for example). Link to comment Share on other sites More sharing options...
Klaynos Posted September 15, 2015 Share Posted September 15, 2015 color = frequency. white light = mixture of frequencies. Why is it that the mixture is always perfect ? (All colors combine to get the notion of white.). My poser is "Why is the perception always the same?" (give or take a few photons....). OK so nothing to do with the human eye then or perception. Your definition of white light doesn't work in my view. You could have a mix of 400nm and 450nm photons, it sure as hell wouldn't be white. Your next point is therefore fundamentally flawed. If you're asking why is the sun always giving white light? Then that is really an artifact of the consistency of emission and evolution, for light bulbs it's consistency and design. Link to comment Share on other sites More sharing options...
swansont Posted September 15, 2015 Share Posted September 15, 2015 . Why is it that the mixture is always perfect ? (All colors combine to get the notion of white.). My poser is "Why is the perception always the same?" (give or take a few photons....). Is it the same? I've noticed this pattern of asking why something is true without establishing that it's actually true. What do you mean by the mixture being perfect? Link to comment Share on other sites More sharing options...
John Cuthber Posted September 15, 2015 Share Posted September 15, 2015 (edited) color = frequency. white light = mixture of frequencies. Why is it that the mixture is always perfect ? (All colors combine to get the notion of white.). My poser is "Why is the perception always the same?" (give or take a few photons....). It isn't really, but your eyes fool you by adjusting automatically. This may help. https://en.wikipedia.org/wiki/Color_balance All the colours you see on a TV or computer screen are made up from mixtures of different amounts of different coloured lights. Almost all of them are not white. The yellow of that smiley face is made from red and green. It's a mixture, but it isn't not white. I have to agree with what others have said . Why do you keep asking "why is...." without checking first if it actually true, even when the evidence is right in front of you?. Edited September 15, 2015 by John Cuthber Link to comment Share on other sites More sharing options...
Klaynos Posted September 15, 2015 Share Posted September 15, 2015 The eye is a terrible sensor. It's nonlinear with ridiculous blank box processing. Link to comment Share on other sites More sharing options...
petrushka.googol Posted September 16, 2015 Author Share Posted September 16, 2015 Physics does not rely on abstractions. I am trying to ascertain the cause as to why the combination of different frequencies in white light is essentially stable. Link to comment Share on other sites More sharing options...
Strange Posted September 16, 2015 Share Posted September 16, 2015 Physics does not rely on abstractions. I am trying to ascertain the cause as to why the combination of different frequencies in white light is essentially stable. What do you mean by "essentially stable"? If you can't explain what you are asking, I don't see how anyone can answer it. "White" light is the subjective impression of a particular mix of frequencies/colours. (Although, as noted, our brains will adjust this so that we still see light as "white" even if it is definitely not white on an object measurement.) You can achieve white in several ways: an equal amount of all frequencies or from just three primary colours (red, green, blue). Link to comment Share on other sites More sharing options...
petrushka.googol Posted September 16, 2015 Author Share Posted September 16, 2015 What do you mean by "essentially stable"? If you can't explain what you are asking, I don't see how anyone can answer it. "White" light is the subjective impression of a particular mix of frequencies/colours. (Although, as noted, our brains will adjust this so that we still see light as "white" even if it is definitely not white on an object measurement.) You can achieve white in several ways: an equal amount of all frequencies or from just three primary colours (red, green, blue). Is it possible to generate an equal amount of all frequencies in the lab ? Link to comment Share on other sites More sharing options...
swansont Posted September 16, 2015 Share Posted September 16, 2015 Physics does not rely on abstractions. LOL. Phyisics is full of abstractions. 2 Link to comment Share on other sites More sharing options...
Strange Posted September 16, 2015 Share Posted September 16, 2015 (edited) Is it possible to generate an equal amount of all frequencies in the lab ? Yes: this was the first search result of many: https://www.rp-photonics.com/white_light_sources.html Physics does not rely on abstractions. I am trying to ascertain the cause as to why the combination of different frequencies in white light is essentially stable. What do you mean by "essentially stable"? If you can't explain what you are asking, I don't see how anyone can answer it. Why is it that the mixture is always perfect ? What do you mean by "perfect"? Edited September 16, 2015 by Strange Link to comment Share on other sites More sharing options...
Klaynos Posted September 16, 2015 Share Posted September 16, 2015 Is it possible to generate an equal amount of all frequencies in the lab ? Supercontinuous sources exist for a given range. What do you mean by all frequencies? Even a single source that does THz to UV is non trivial. If even possible. And equal amount, amount of what? Photons, energy, intensity? 1 Link to comment Share on other sites More sharing options...
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