Q. In the visible region the dispersive powers and the mean angular deviations for crown and flint glass prisms are $\omega,\omega'$ and $d,\ d'$ respectively. The condition for getting deviation without dispersion when the two prisms are combined is
A) $\sqrt{\omega d} + \sqrt{\omega'd'} = 0$
B) $\omega^{'}d + \omega d^{'} = 0$
C) $\omega d + \omega^{'}d^{'} = 0$
D) $(\omega d)^{2} = \left( \omega^{'}d^{'} \right)^{2} = 0$
Explanation
(c) $\theta_{net} = \theta + \theta^{'} = 0 \Rightarrow \omega d + \omega^{'}d^{'} = 0$
($\theta =$ Angular dispersion $= \omega.\ \delta_{y})$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.