We define linear magnification (m) as the
ratio of the height of the image (h¢) to the height of the object (h):
m = 
h
h
′
(9 8)
h and h¢ will be taken positive or negative in accordance with the accepted
sign convention In triangles A¢B¢P and ABP, we have,
B A
B P
BA
BP
′
′
′
=
With the sign convention, this becomes
Rationalised 2023-24
Physics
226
–
–
h
v
h
u
′ = –
so that
m = 
–
h
v
h
u
′ =
(9 9)
We have derived here the mirror equation, Eq