Question

A light ray is incident normally on one of the refracting faces of a prism and just emergence out grazing the second surface. then, the relation between angle of the prism and its critical angle is

• A. $A=C$
• B. $A\ne C$
• C. $A<C$
• D. $A>C$

Answer 1

The correct option is A $A=C$

From the figure following the line $ABC$ we can write

$\left({90}^{\circ }-A\right)+C+{90}^{\circ }={180}^{\circ }$

$\Rightarrow C-A+{180}^{\circ }={180}^{\circ }$

$\Rightarrow C-A=0$

$\Rightarrow C=A$

Hence the correct answer is option (A).