7
Rationalised 2023-24
Physics
238
 EXAMPLE 9 8
1
1
1
v
u
f
−
=
so that we get
1
2
1
1
1
f
f
f
=
+
(9 30)
The derivation is valid for any number of thin lenses in contact If
several thin lenses of focal length f1, f2, f3,