Q. A biconvex lens form a real image of an object placed perpendicular to its principal axis. Suppose the radii of curvature of the lens tend to infinity. Then the image would
A) Disappear
B) Remain as real image still
C) Be virtual and of the same size as the object
D) Suffer from aberrations
Explanation
(c) $\frac{1}{f} = (\mu - 1)\left( \frac{1}{R_{1}} - \frac{1}{R_{2}} \right)$
For biconvex lens $R_{2} = - R_{1}\ \therefore\frac{1}{f} = (\mu - 1)\left( \frac{2}{R} \right)$
Given $R = \infty\ \ \therefore f = \infty,$ so no focus at real distance
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.