Cauchy ’ s Formula
Critical Angle
The angle of incidence in a denser medium for which the angle of refraction in rarer medium becomes 90 °. is called critical angle ( C ).
Critical angle for diamond = 24 ° Critical angle for glass = 42 ° : Critical angle for water = 48 ° :
Refractive index of denser medium μ = 1 / sin C
Total Internal Reflection ( TIR )
When a light ray travelling from a denser medium towards a rarer medium is incident at the interface at an angle of incidence greater than critical angle , then light rays reflected back in to the denser medium . This phenomena is called TIR .
Critical angle increases with temperature .