Q. The power of an achromatic convergent lens of two lenses is +2 D. The power of convex lens is +5 D. The ratio of dispersive power of convex and concave lenses will be
A) 5:3
B) 3:5
C) 2:5
D) 5:2
Explanation
(b) Here, $P_{1} + P_{2} = 2D\ and\ P_{1} = 5D$
So $P_{2} = \ - 3\ D$
For an achromatic combination
$\omega_{1}P_{1} + \omega_{2}P_{2} = 0$
$or\ \ \ \frac{\omega_{1}}{\omega_{2}} = \left( - \frac{P_{2}}{P_{1}} \right) = - \frac{( - 3)}{2} = \frac{3}{5}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.