How is magnification (m) related to the distance of the object (u) and the distance of the image (v) ?

$\text{Magnification (m)} = \dfrac{\text{Length of image (I)}}{\text{Length of object (O)}} \\[0.5em] = \dfrac{\text{Distance of image (v)}}{\text{Distance of object (u)}} \\[1em] \text{OR} \\[1em] m = \dfrac{I}{O} = - \dfrac{v}{u}$

where

'I' is the length of the image,
'O' is the length of the object,
'v' is the distance of the image,
'u' is the distance of the object.