Index matching is used in liquid-liquid and liquid-solid ([[Multiphase flow]]) experimental systems to minimise the distortions that occur in these systems,<ref>{{cite journal|title=A review of solid–fluid selection options for optical-based measurements in single-phase liquid, two-phase liquid–liquid and multiphase solid–liquid flows|authorsauthor=Wright, S.F., |author2=Zadrazil, I. & |author3=Markides, C.N. |journal=Experiments in Fluids |year=2017|volume=58 |issue=9|pagespage=108|bibcode=2017ExFl...58..108W|doi=10.1007/s00348-017-2386-y|doi-access=free}}</ref> this is particularly important for systems with many interfaces which become optically inaccessible. Matching the refractive index minimises [[reflection (physics)|reflection]], [[refraction]], [[diffraction]] and rotations that occurs at the interfaces allowing access to regions that would otherwise be inaccessible to optical measurements. This is particularly important for advanced optical measurements like [[Laser-induced fluorescence]], [[Particle image velocimetry]] and [[Particle tracking velocimetry]] to name a few.
