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MISCO Refractometer Technical Support  

Refraction and Index of Refraction

Snell's Law: Snell's Law uses the Index of Refraction for each medium to determine the angle of refraction when light passes from one medium to another. Snell's Law states:

n1 is the Index of Refraction of the medium for the incident ray.
n2 is the Index of Refraction of the medium for the refracted ray.
q1 is the Angle of Incidence.
q 2 is the Angle of Refraction.

Law of Reflection - q1' = q1
Law of Refraction - n1sinq1 = n2sinq2      (Snell's Law) 

Here the "n's" are constants called the index of refractions.  These constants are obtained by the dividing the speed of light (c) by the actual velocity of the light traveling in the medium (v), in other words 
( c / v ).  Below is a table of some common indices of refraction.

 

 
Medium Refractive Index Medium Refractive Index
Vacuum exactly 1 Typical Crown Glass 1.52
Air (STP) * 1.00029 Sodium Chloride (salt) 1.54
Water (20o) 1.33 Polystyrene 1.55
Acetone 1.36 Carbon Disulfide 1.63
Ethyl Alcohol 1.36 Heavy Flint Glass 1.65
Sugar Solution (30%) 1.38 Sapphire 1.77
Fused Quartz 1.46 Heaviest Flint Glass 1.89
Sugar Solution (80%) 1.49 Diamond 2.42