Hi all.

Photons transitioning from air into yellow tinted water decelerate the same amount if entering green tinted water ?

Or, a red color light beam and a violet color light beam get different deceleration entering into clear water ? What changes crossing trough media ? Its energy, its wavelenght, both, other ?

Do photons crossing into a rainbow outputted by a prism experience several changes of speed according the color they are crossing ?

(high chance for poor terminology above 😟)

1 hour ago, Externet said:

Photons transitioning from air into yellow tinted water decelerate the same amount if entering green tinted water ?

Photons do not experience deceleration or acceleration. What happens in a medium other than vacuum is basically that they start interacting with electrons present there; you could perhaps say (not entirely rigorously) that they get absorbed and re-emitted, the process of which leads to a tiny but measurable delay. So the overall measured speed appears to be lower, even though the photons themselves always locally propagate at exactly c. But there is never any deceleration involved, since massless particles cannot travel at anything other than exactly c.

7 hours ago, Externet said:

What changes crossing trough media ? Its energy, its wavelenght, both, other ?

The wavelength.

9 hours ago, Markus Hanke said:

Photons do not experience deceleration or acceleration. What happens in a medium other than vacuum is basically that they start interacting with electrons present there; you could perhaps say (not entirely rigorously) that they get absorbed and re-emitted, the process of which leads to a tiny but measurable delay. So the overall measured speed appears to be lower, even though the photons themselves always locally propagate at exactly c. But there is never any deceleration involved, since massless particles cannot travel at anything other than exactly c.

I've never liked the 'absorption - delayed emission' explanation of refraction. Such an explanation would be expected to produce scattering as well as failing to account for the particular property of materials that produce higher refractive indices than other materials. I wrote the following about six months ago. It would appear that I thought I would need it again:

This is a common misunderstanding of refraction. Refraction is easiest to understand in terms of classical electromagnetic waves. This can then be translated to the quantum picture provided the important aspects of the classical picture are maintained. When an electromagnetic wave passes through a medium, it exerts a force on the charges and charge dipoles of the medium. Depending on how easily the charges and charge dipoles of the medium can move in response to this force, the motion of the charges and charge dipoles of the medium creates an electromagnetic wave that combines with the original electromagnetic wave to produce a total electromagnetic wave that is delayed with respect to the original electromagnetic wave and therefore travels through the medium at a slower speed. Thus, the refractive index of the medium depends on how readily the charges and charge dipoles of the medium can respond to the passing electromagnetic wave. This depends on the frequency of the passing electromagnetic wave. Higher frequencies exert a greater force, but larger bulkier charges and charge dipoles respond more to lower frequencies. At visible frequencies, only electrons can significantly respond to the passing electromagnetic wave, and in this case, the refractive index depends on the polarisablity of the electron orbitals of the medium and increases with frequency due to the increasing energy of the photons.

As for the question asked in the opening post about light passing through an absorbing medium, this can actually be somewhat complicated as one can get weird dispersion effects near absorption frequencies. These weird dispersion effects are sometimes reported as causing faster-than-c propagation of light through the medium. A proper understanding of the effects of dispersion requires an understanding of the notions of phase velocity and group velocity.

10 hours ago, Externet said:

Do photons crossing into a rainbow outputted by a prism experience several changes of speed according the color they are crossing ?

Light passing through light does nothing (photons at very high energy can scatter off of each other, but it’s rare)