Total internal reflection occurs in denser medium when light is incident at surface of separation at an angle exceeding critical angle of the medium.

Given $\mathrm{i}=45°$ in the medium and total internal reflection occurs at the glassair interface

$\therefore$  $\mathrm{n}>\frac{1}{\text{sin C}}>\frac{1}{\sin 45°}=\sqrt{2}$

$\mathrm{n}>\sqrt{2}$