We define an angle ic by the following equation
2
1
sin c
n
i
=n
(10 8)
Thus, if i = ic then sin r = 1 and r = 90° Obviously, for i > ic, there can
not be any refracted wave The angle ic is known as the critical angle and
for all angles of incidence greater than the critical angle, we will not have
any refracted wave and the wave will undergo what is known as total
internal reflection