6), we get
–
–
v–
f
v
f
u
+
= –
or
v–
f
v
f
u
=
      v
f
uv
=
+
1
Dividing it by v, we get
      
1
1
1
v
u
f
+
=
(9 7)
This relation is known as the mirror equation The size of the image relative to the size of the object is another
important quantity to consider 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