For glass, the angle is 42

^{o}. For diamond, it is 24

^{o}. This is what makes

diamond so nice and pretty and sparkly.

There is an equation which will link the differences in optical density to the critical angle (the name of the angle at which total internal reflection will occur)...

Convert Critical Angle into Index of Refraction

**1/(sin ***angle*)

Convert Index of Refraction to Critical angle

**sin**^{-1} *i*^{-1}

*The first *^{-1} is the **inverse** of sine (which converts the ratio of two sides to the angle) and the second ^{-1} is the reciprocal of the index of refraction.

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