Question

A prism has a refracting angle of $60^{\circ}$. When placed in the position of minimum deviation, it produces a deviation of $30^{\circ}$. The angle of incidence is

• A. $30^{\circ}$
• B. $45^{\circ}$
• C. $15^{\circ}$
• D. $60^{\circ}$

Answer 1

Answer: (B)

$\mu=\frac{\sin i}{\sin r}=\frac{\sin \left(\frac{\delta +A}{2}\right)}{\sin (A / 2)}$
$r=A / 2$
$\frac{\sin (i)}{\sin (A / 2)}=\frac{\sin \left(\frac{\delta +A}{2}\right)}{\sin (A / 2)}$
$i=(\delta+A) / 2$
$=\frac{30+60}{2}$
$=45^{\circ}$