A prism of refractive index $\sqrt{2}$ and apex angle A is shown. Light is incident from PQ side at angle of incidence i $(0<i\le 90°)$

 

If A = 80° then light incident at some angle will emerge from surface PR and at some other angles light will suffer TIR at surface PR.

If $A=92°$ then light incident at all angles will be reflected back from surface PR

Whatever is the value of A, light will emerge from the surface PR for some value of i.

If A = 40° then light incident at all angles will emerge from surface PR