An object is placed at 15 cm from a convex lens of focal length 10 cm. Where should another convex mirror of radius 12 cm placed such that image will coincide with object.

Options

A. 18 cm
B. 17 cm
C. 14 cm
D. 20 cm

Answer

A

Explanation

(a) For image coincide with object
(i) Concave mirror with convex lens concave mirror should be placed at (v + R)
(ii) Convex mirror with convex lens convex mirror should be placed at (v - R)
Hence, `(1)/(v) = (1)/(f) + (1)/(u) = (1)/(10) - (1)/(15) = (3-2)/(30) v = 30`
for convex mirror
i.e, v - R = 30 - 12 = 18 cm.