I know this sounds like an inane question, but I have a real scientific motive behind it (a fly mutant with red eyes, where the actual pigment is yellow when extracted). Strangly enough, I can’t find anything in the literature about this. I assume that in quantity, there is a greater absorption of green light, making the stuff appear red, and when diluted, there is less absorption and greater transmission of yellow, making the stuff appear yellow. I need a Real Physical Explaination.
I call out to all the physisists out there. If you could point me to a reference in the peer-revied literature or even a textbook, I would appreciate it.
Thanks,
MM
I’m not a physicist and I didn’t find a reference to a peer-reviewed paper, so I doubt if this will be relevant, but there’s a very simplified explanation of the yellow/red dye phenomenon on this page (beware, very slow loading PDF): http://www.opticsforkids.org/resources/Color_2.pdf. At the end of the article, there are a couple of references to optics texts which might be of use.
IANAP,IAAC,
At a guess:
Low conc. of yellow dye: Many wavelengths reach the chromophore, green and blue are absorbed, some red absorbed, very little yellow absorbed, mostly yellow reflected. Easy. Remember this is a curve of wavelength versus absortion - not a clear cut delineation.
High conc. of yellow dye: There is a far greater scattering of all wavelenths which are reflected. Some yellow is absorbed during ‘each scattering’. Each time the reflected light is scattered all colours are attenuated even further. However, red has a longer wavelenght than yellow and will scatter less. Sunset effect.
Thus, it is more PROBABLE that a red photon will enter the bottle and come out ‘unscathed’. A yellow one will bounce around a bit more - each time having a chance of being absorbed. This greater exposure of the yellow photon to an absorption event outweighs the reds initial greater absorption by the chromophore. So not that many yellows make it out of the bottle/fly eye.
The light will not penetrate the bottle far, this will all be happening just inside the glass-liquid boundary.
Check up Raleigh scattering and distribution of electronic transitions based on vibration of energy levels.
I bet it’s a pretty dye for a fly eye.
IANAP,IAAC,
At a guess:
Low conc. of yellow dye: Many wavelengths reach the chromophore, green and blue are absorbed, some red absorbed, very little yellow absorbed, mostly yellow reflected. Easy. Remember this is a curve of wavelength versus absortion - not a clear cut delineation.
High conc. of yellow dye: There is a far greater scattering of all wavelenths which are reflected. Some yellow is absorbed during ‘each scattering’. Each time the reflected light is scattered all colours are attenuated even further. However, red has a longer wavelenght than yellow and will scatter less. Sunset effect.
Thus, it is more PROBABLE that a red photon will enter the bottle and come out ‘unscathed’. A yellow one will bounce around a bit more - each time having a chance of being absorbed. This greater exposure of the yellow photon to an absorption event outweighs the reds initial greater absorption by the chromophore. So not that many yellows make it out of the bottle/fly eye.
The light will not penetrate the bottle far, this will all be happening just inside the glass-liquid boundary.
Check up Raleigh scattering and distribution of electronic transitions based on vibration of energy levels.
I bet it’s a pretty dye for a fly eye.
The professor’s point in the article is that light that’s largely absorbed by one filter will be very largely absorbed by another filter of the same color. On the other hand, light that’s mostly transmitted will be mostly transmitted the second time, too. This changes the overall color of the light.
This is a round about way of saying that light is not absorbed proprotionately in all wavelengths as a filter becomes stronger (thicker). It doesn’t take much of the yellow dye at all to change the color – as can be seen tilting the bottle so the part draining down the side is momentarily thicker.
One reason this isn’t completely intuitive is there are filters that when a couple are stacked together don’t produce a very noticable color change. I just tried stacking plastic three yellow filters together that even when doubled over didn’t change the yellow all that much. But another yellow filter in the set changes the color to orangish.
Nothing much to add, just wanted to mention that saffron works like that too.