Question

A point source S is placed midway between two converging mirrors having equal focal length f as shown in figure. Find the values of d for which only one image is formed.
Figure

Answer 1

Given,
Two converging mirrors having equal focal length 'f '.
Both the mirrors will produce one image under two conditions:

Case-1
When the point source is at the centre of curvature of the mirrors, i.e, at a distance of '2f ' from each mirror, the images will be produced at the same point 'S'. Therefore, d = 2f + 2f = 4f


Case-II
When the point source 'S' is at focus, i.e., at a distance 'f ' from each mirror, the rays from the source after reflecting from one mirror will become parallel and so these parallel rays, after the reflection from the other mirror the object itself. Thus, only one image is formed.
Here d = f + f = 2f