Question

An equilateral prism is kept in the minimum deviation position. If the angle of incidence of a monochromatic ray at a refracting face is ${49}^0{30}^{\prime }$ the angle of minimum deviation of the ray will be:

• A. ${39}^0$
• B. ${49}^0{30}^{\prime }$
• C. ${40}^0{30}^{\prime }$
• D. ${51}^0$

Answer 1

The correct option is A ${39}^0$

Given that:

Angle of incidence, $i={49}^0{30}^{\prime }$

Angle of prism, $A={60}^0$

Angle of deviation: $D=2i-A$
$=2\times {49}^0{30}^{\prime }-60={39}^0$