Answer
(a) $f_1$
(b) $M_1=6.0; M_2=2.92$
Work Step by Step
(a) We know that $M=\frac{N}{f}$. This equation shows that magnification and focal length are mutually inversely proportional. Thus, if the focal length is decreased then the magnification increases. Now, we can conclude that the lens with focal length $f_1=5.0cm $ produces greater magnification.
(b) The maximum magnification of the first lens is given as
$M=1+\frac{N}{f}$
We plug in the known values to obtain:
$M=1+\frac{25cm}{5cm}$
$M=6.0$
The maximum magnification of the second lens is given as
$M=1+\frac{N}{f}$
We plug in the known values to obtain:
$M=1+\frac{25cm}{13cm}$
$M=2.92$
