Light can be made sort of visible, when volume scatter is used. I want this light to split into different colors once it has passed a prism in an appropriate angle.
In a second step, I would like to simulate a rainbow that is really created by a particle system of rain drops.
Is there any chance, this could be realized in blender?
There are various ways of achieving refractive dispersion in cycles (there are lots of threads on the subject here) - however, Cycles isn’t very good at dealing with such effects.
Cycles isn’t a spectral renderer. It’s also a straight path tracing engine, which means it doesn’t deal with refractive caustics very well either.
Cycles probably isn’t the best tool if you want to really explore such effects. Maybe somebody can point you in the direction of a better renderer for such things.
I think people would use luxcorerender.
I can tell you if you use some physics knowledges and node. You can actually get a shader with spectrum so you can render a dispersion glass shader in Cycles.
You can search the Cauchy Formula in Wikipedia and it will tell you what true meaning of IOR and dispersion are of an object.
But the Cycles renderer are not designed for rendering dispersion and caustics because Cycles use such “Random” patterns that are actually “Brute Force” (Or you can use the Path Guiding when rendering in CPU in 3.4+, but still ineffectively)
The best solution of this question is using LuxCore render engine because LuxCore using some special algorithm such as Bidirectional Engine and Metropolis patterns that can focus on rendering dispersion/refraction/caustic etc. LuxCore is pretty easy to get started and it also supports Cycles
nodes, too.