Question

A luminous object is placed at a distance of 30 cm from the convex lens of focal length 20 cm.The distance from the lens a convex mirror of radius of curvature 10 cm should be placed on the other side of the lens such that the real images formed on the source itself is

• A. $12cm$
• B. $30cm$
• C. $50cm$
• D. $60cm$

Answer 1

The correct option is C $50cm$

for the final image to be formed at the source the image of the image through the lens should form at the central of the mirror.

$\frac{1}{\vartheta }-\frac{1}{(-30)}=\frac{1}{20}$

$\frac{1}{\vartheta }=\frac{1}{20}-\frac{1}{30}$

$\frac{1}{\vartheta }=\frac{10}{600}$

$\vartheta =60cm$

$d=60-10=50cm$