Here fo = 2cm, fe = 5cm, uo = 2.4cm, ve = D = 25cm.
In normal use, magnifying power
M = \(-\frac{v_o}{u_o}(1+\frac{D}{f_e})\)
For objective, \(\frac{1}{f_o}=\frac{1}{v_o}-\frac{1}{u_o}\)
\(\frac{1}{2}=\frac{1}{v_o}-\frac{1}{(-2.4)}\)
\(\frac{1}{v_e}=\frac{1}{2}-\frac{1}{2.4}=\frac{6-5}{12}\)
ve = 12cm
So, M = \(-\frac{12}{24}(1+\frac{25}{5})\)
= −5 × 6 = −30