Sorry, my fault for not being very specific.
The point im getting at is why would light travel in a straight line through a medium at a slower observed velocity than in a vacuum, if the reason for this is the absorption and almost immediate re-emission of the photons in a random direction.
Wouldn't this create a scattering effect?
in fact every material creates a scattering effect. that's why you're able to see a laser beam from the side if it goes through eg a liquid. the amount of scattering is dependant of the wavelenght and size of the particles. interestingly the distribution of intensity is highly directional - most of the intensity will arrive where you'd expect the ray to leave the material if you assumed a straight line. the math behind these things is very unfunny so don't ask for it
(in short: you sum up a lot of spherical waves and end up with something non spherical. but again: that's very complicated, people have won nobel prizes for these things)
these thoughts should hold true for absorption and reemission as the mathematical approach seems to be similar so i think huge scattering effects should pose no problem. but another thing i thought of is the time factor: in the literature i had at hand i found no explanation on how long absorption and emission take based on the material and why there are differences regarding different wavelenghts (dispersion).