# Linear magnification of a spherical mirror (m):

m = size of image (h₂)/size of object (h₁) = A’B’/AB

(a) For a concave mirror:

From the above Figure      A’B’/AB = PB’/PB

When a real and inverted image is formed; A’B’ = -h₂, AB = +h₁

PB’ = -v, PB = -u

∴ -h₂/h₁ = -v/-u = v/u

∴ m = h₂/h₁ = -v/u      i.e. m is negative

When a virtual and erect image is formed;

A’B’ = +h₂, AB = +h₁

PB’ = +v, PB = -u