A ray of light is incident from a denser to a rarer medium. The critical angle for total internal reflection is ${\mathrm{\theta }}_{\text{iC}}$ and Brewster's angle of incidence is ${\mathrm{\theta }}_{\text{iB}}$, such that $\frac{\text{sin}{\mathrm{\theta }}_{\text{iC}}}{\text{sin}{\mathrm{\theta }}_{\text{iB}}}=\mathrm{\eta }=1\text{.}28$. The relative refractive index of the two media is