Question

A parallel beam of monochromatic light is incident at one surface of a equilateral prism. Angle of incidence is ${55}^o$ and angle of emergence is ${46}^o$. The angle of minimum deviation will be

• A. Less than ${41}^o$
• B. Equal to ${41}^o$
• C. More than ${41}^o$
• D. None of the above

Answer 1

Answer: (A)

Less than ${41}^o$

By the hypothesis, we know that
$i_1+i_2=A+\delta \Rightarrow {55}^o+{46}^o={60}^o+delta\Rightarrow \delta ={41}^o$
But ${\delta }_m<\delta$, so ${\delta }_m<{41}^o$