When an object is placed normally on the principal axis of a spherial mirror at a distance 'a' from its pole, its image is formed at a distance 'v' from the pole of mirror such that `(1)/(v)+(1)/(u)=(1)/(f)`, where f = focal length of given mirror.
The relation is called mirror formula and is true for all types of mirrors under all conditions. However, values of u, v and f must be put with proper signs are per the sign convention followed. If 'h' be the height of the linear object and h' the height of image, then ratio `(h')/(h)` is called linear magnification or lateral magnification and its value m is given as :
`m=(h')/(h)=-(v)/(u)`
A small match box lies along the principal axis of a concave mirror and one end of match box is at centre of curvature of the mirror. Draw a ray diagram to show its image. Is its magnetification uniform?

Explanation

Ray diagram Fig. 9.13 is shown here. A. B. is the image of the match box AB. Its magnification is non - uniform i.e., the image is distored.