Q. A achromatic combination is made with a lens of focal length $f$ and dispersive power $\omega$ with a lens having dispersive power of $2\omega$. The focal length of second will be
A) $2\ f$
B) $f/2$
C) $- f/2$
D) $- 2\ f$
Explanation
(d) $\omega/f = - \omega/f' \Rightarrow f' = - 2f$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.