∞ generated and posted on 2016.01.13 ∞
Description of the relative speed of light as light moves through a substance.
As light slows or increases in speed it bends, resulting in a fuzziness during microscopy if light is allowed to pass through multiple substances not all of which have the same index of refraction, such as glass versus air.
The use of oil immersion during light microscopy is a means of avoiding this problem, and thereby increasing resolution, since glass and mineral posses approximately the same index of refraction.