Q. The focal lengths of convex lens for red and blue light are $100\ cm$ and 96.8 $cm$ respectively. The dispersive power of material of lens is
A) 0.325
B) 0.0325
C) 0.98
D) 0.968
Explanation
(b) $\omega = \frac{f_{R} - f_{V}}{f_{y}} = \frac{f_{R} - f_{V}}{\sqrt{f_{V}f_{R}}}$
Putting value of $f_{V}$ and $f_{R}$ we get $\omega = 0.0325$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.