Rationalised 2023-24
Physics
242
m
uv
v v
f
fv
=
=



 = 



1
1
1
–
–
Now according to our sign convention, v is negative, and is equal in
magnitude to D Thus, the magnification is
m
fD
=
+

1
(9 39)
Since D is about 25 cm, to have a magnification of six, one needs a convex
lens of focal length, f = 5 cm Note that m = h¢/h where h is the size of the object and h¢ the size of
the image