)The phase advance of the "p" component relative to the "s" component is then given by
This is plotted in black in Fig.2, for angles of incidence exceeding the critical angle, for three values of the refractive index.It can be seen that a refractive index of 1.45 is not enough to give a 45° phase difference, whereas a refractive index of 1.5 is enough (by a slim margin) to give a 45° phase difference at two angles of incidence