Optics Question 603
Question: A biconvex lens forms 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
[MP PET 1994]
Options:
A) Disappear
B) Remain as real image still
C) Be virtual and of the same size as the object
D) Suffer from aberrations
Show Answer
Answer:
Correct Answer: C
Solution:
$ \frac{1}{f}=(\mu -1)( \frac{1}{R _{1}}-\frac{1}{R _{2}} ) $ For biconvex lens $ R _{2}=-R _{1} $
$ \therefore $ $ \frac{1}{f}=(\mu -1)( \frac{2}{R} ) $ Given $ R=\infty $
$ \therefore $ $ f=\infty $ , so no focus at real distance.
