Write the lens formula and its magnification.

Lens formula
The lens formula is ,

Where
v = distance of the image formed from the optical center of the lens,
u = the distance of the object from the optical centre of the lens
f= the focal length of the lens.
Magnification

The ratio of the height of an image (h_i) to the height of an object (h_o) is defined as the magnification of a lens.
Also, magnification is equal to the ratio of image distance to that of object distance.

m= Magnification of the lens,

h_i = Height of image from Principal axis,

h_o= Height of object from principle axis,

v= Image distance from optical center,

u= Object distance from optical center,