CBSE Class 10 Science 2017 · Paper 31/1 · Question 23

(a) The mirror is a convex mirror: for every position of the object it forms a virtual, erect and diminished image behind the mirror, between $P$ and $F$ (see the ray diagram). Use: convex mirrors are used as rear-view (wing) mirrors in vehicles, because they always give an erect, though diminished, image and, being curved outwards, have a wider field of view, so the driver sees a larger area behind. (b) The radius of curvature of a spherical mirror is the radius of the sphere of which its reflecting surface is a part; it is the distance between the pole and the centre of curvature. For $R=+24$ cm the centre of curvature lies behind the mirror, so the mirror is convex, and its focal length is $f=\frac{R}{2}=+12$ cm.