Q. A thin prism $P\ $of refracting angle $3{^\circ}\ $and refractive index 1.5 is combined with another thin prism $Q$of refractive index 1.6 to produce dispersion without deviation. Then the angle of prism $Q$ is
A) $3{^\circ}$
B) $4{^\circ}$
C) $3.5{^\circ}$
D) $2.5{^\circ}$
Explanation
(d) Given refracting angle of prism $P$
$A_{P} = 3{^\circ}$
And refractive index of prism $P$
$\mu_{P} = 1.5$
And refractive index of prism $Q$
$\mu = 1.6$
$\left( \mu_{P} - 1 \right)A_{P} = \left( \mu_{0} - 1 \right)A_{Q}$
$(1.5 - 1)3{^\circ} = (1.6 - 1)A_{Q}$
Or $0.5 \times 3 = 0.6 \times A_{Q}$
Or $A_{Q} = \frac{0.5\ \times \ 3}{0.6}$
Or $A_{Q} = 2.5{^\circ}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.