Q. A thin prism of angle $15{^\circ}$ made of glass of refractive index $\mu_{1} = 1.5$ is combined with another prism of glass of refractive index $\mu_{2} = 1.75$. The combination of the prisms produces dispersion without deviation. The angle of the second prism should be
A) $12{^\circ}$
B) $5{^\circ}$
C) $7{^\circ}$
D) $10{^\circ}$
Explanation
(d) Deviation = zero
So, $\delta = \delta_{1} + \delta_{2} = 0$
$\left( \mu_{1} - 1 \right)A_{1} + \left( \mu_{2} - 1 \right)A_{2} = 0$
$A_{2}(1.75 - 1) = - (1.5 - 1)15{^\circ}$
$A_{2} = - \frac{0.5}{0.75} \times 15{^\circ} \Rightarrow A_{2} = - 10{^\circ}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.