A luminous object is placed at a distance of 30 cm from the convex lens of focal length 20 cm . On t

Question

A luminous object is placed at a distance of 30 cm from the convex lens of focal length 20 cm . On the other side of the lens, at what distance from the lens a convex mirror of radius of curvature 10 cm be placed in order to have an upright image of the object coincident with it?\

Professor PC Thomas Classes · Answer

(a): For lens, $\frac{1}{v}-\frac{1}{u}=\frac{1}{f}$ $$ u=-30, f=20, v=60 \mathrm{~cm} $$ To have an upright image of the object, coincide with it, image should tend to form at centre of curvature of convex mirror. Therefore, the distance of convex mirror from the lens $=60-10=50 \mathrm{~cm}$.\