Define ‘refractive index of a transparent medium.’ What is its unit? Which has a higher refractive index, glass or water?
Refractive index of transparent medium is defined as the ratio of speed of light in vacuum to the speed of light through medium.
Refractive index (n) = 
Where;
C = speed of light;
V = speed of light in medium;
It has no unit because it is the ratio of two quantities of same type (speed);
Glass has higher refractive index of 1.52. (Because Refractive index of water = 1.33).
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