# The Lens Formula and Magnification

The lens formula is a relation between the focal length of the lens and the object and image distances from it. This relation is (for both convex and concave lenses)

------------- (10.8)

Height of the image (hâ€™)

m = Height of the object (h) --------------- (10.9)

Also Magnification (m) =    ----------- (10.10)

U = the object distance

V = the image distance  All are measured from the optic centre of the lens

F = focal length of the lens

f = the focal length

h1 = the height of the object

h2 = the height of the image

m = the linear magnification, defined as the ratio of the height of the image to the height of the object.