CATION OF A LENS       The magnification of a lens may be defined as the ratio of the size (height) of the image to the size (height) of the object. The magnification of a lens is represented by the letter ‘m’. Thus,           m   =   size of the image / size of the objector          m   =   h2/h1       Where,   h2   =   size of image                     h1   =   size of object       The magnification (m) of lens can also be calculated in terms of image distance (v) and object distance (u), if we do not know the size (height) of object and image. Thus,           m   =   image distance / object distance          m   =   v/u       Where,   v   =   image distance                     u   =   object distance       PLEASE note that the magnification formula is APPLICABLE both in CONVEX lenses and CONCAVE lenses. And the magnification m is positive when the image formed is virtual and erect. On the other hand, the magnification m is negative when the image formed is real and inverted. hope it HELP you