$(a)\;100\;times \\ (b)\;120\;times \\ (c)\;140\;times \\ (d)\;75\;times $

Length of tube $=25\;cm$

$f_e =2.5 cm$

we have $v_0 +f_e =L$

$v_0 =25 -2.5 =22.5 \;cm$

Also

$\large\frac{1}{v_0} -\frac{1}{u_0} =\frac{1}{f_0}$

$\large\frac{1}{22.5} -\frac{1}{40} =\frac{1}{1.5}$

$u_0 = 1.6 \;cm$

magnification =$\large\frac{v_0}{u_0} \times \frac{D}{f_e}$

$\qquad= \large\frac{22.5}{1.6} \times \frac{22}{2.5}$

$\qquad=140$

Hence c is the correct answer

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