A light ray is incident on lower medium boundary at an angle $30°$ with the normal. Which of following statement is/are true?

For T.I.R at $A$

$$\begin{gathered} 4 \sin 30°={\mu }_2 \sin 90° \\ {\mu }_2=2 \end{gathered}$$

Case - I

If ${\mu }_2<2$ then critical angle at surface B is less than ${30}^0$ and hence  T.I.R takes place & in this situation angle of deviation is $120°$.

Case - II

If ${\mu }_2>2$, then critical angle  at surface A is greater than ${30}^0 and in this case ,$

$4 \sin {30}^0=2 \sin e \Rightarrow e ={90}^0$

So angle of deviation = ${90}^0-{30}^0={60}^0$