Define Magnification of a lens.

Explanation

It is defined as the ratio of the heigh of the image to the height of an object . Magnification is denoted by the letter .m. If height of the object is h and height of the image is h , the magnification produced by lens is ,
`m=("height of the image")/("height of the object")=(h)/(h)`
Also it is related to the distance of the object (u) and the distance of the image (v) as follows:
`m=("distance of the image")/("distance of the object")=(v)/(u)`