Dan zal ik het wel niet helemaal begrijpen, maar
"Foucault, die aantoonde dat de voortplantingssnelheid van het licht door een medium inderdaad afneemt" zet me dan op het verkeerde been !
De voortplantingssnelheid neemt inderdaad af, maar dat is de voortplantingssnelheid van de lichtgolf door het medium. Die neemt af naarmate de optische dichtheid van het medium toeneemt. De lichtdeeltjes, de fotonen dus, bewegen gewoon met de lichtsnelheid.
Hoe kan dat? Dit wordt uitgelegd in de volgende quote, die komt van
http://online.cctt.org/ph...onoflight/refraction.asp"Those electrons which are free to vibrate without striking neighboring atoms complete two quantum mechanical processes: excitation and de-excitation. Excitation occurs when a ground state electron absorbs a photon and jumps up to a higher, unstable energy level. Photons are bundles of radiant energy that represent the particle nature of light. The amount of energy present in a photon is calculated with the equation E = hf where f is the frequency of the light wave and h is Planck's constant, 6.64 x 10-34 J sec. When the electron falls back to its ground state it releases a photon. The energy of the released photon exactly match the difference in the electron energy states and the energy of the initially absorbed electron. This process is called de- excitation. The photon emitted is then free to travel at 3 x 108 m/sec until it is again absorbed by another electron. There is no energy lost in the process. The closer the energy of the photon is to a difference in the fundamental energy states of the atom, the more interaction takes place. Since the energy of the emitted photon exactly equals the energy of the absorbed photon, the frequency of the photons/light does not change. However, the time delay caused by this absorption/readmission process increases the time required for a photon to travel through the medium and therefore results in a slower average speed of light in that particular medium. The amount of time delay is evidenced by the optically dense medium's index of refraction; the greater the value of n, the more interaction and the greater the amount of refraction.