## Question

A small strip of plane mirror *A* is set with its plane normal to the principal axis of a convex mirror *B* and placed 15 cm in front of *B* which it partly covers. An object is placed 30 cm from *A* and the two virtual images formed by reflection in *A* and *B* concide without parallax. Find the radius of curvature of *B*.

### Solution

45 cm

are virtual images of object *PQ* due to reflections in *A* and*B* respectively. Since the image of object *PQ* due ot reflection from plane mirror *A* is as far behind the mirror as the object is in front of it, the image distance for the convex mirror *B* is

Object distance

Which gives *f* = 22.5 cm

Hence *R* = 2*f* = **45 cm**

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