Optics 4 Question 15
16. A ray of light is incident normally on one of the faces of a prism of apex angle $30^{\circ}$ and refractive index $\sqrt{2}$. The angle of deviation of the ray is …… degrees.
(1997, 2M)
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Solution:
- Ray falls normally on the face $A B$. Therefore, it will pass undeviated through $A B$.
$\therefore r _2=90^{\circ}-60^{\circ}=30^{\circ}$
$$ \begin{aligned} & \mu=\sqrt{2}=\frac{\sin i _2}{\sin r _2} \\ & i _2=45^{\circ} \end{aligned} $$
Deviation $=i _2-r _2=45^{\circ}-30^{\circ}=15^{\circ}$
(Deviation at face $A C$ only)
