Scientific Volume Imaging b.v.
The refractive index (r.i.) of a material is the factor by which electromagnetic radiation is slowed down (relative to vacuum) when it travels inside the material. (Source: Wikipedia).
In optical microscopy, important r.i. are the Lens Refractive Index and the Medium Refractive Index. A mismatch between these two indices will cause several serious problems, see Refractive Index Mismatch.
