In case of a compound microscope, an angular magnification of $30X$ is to be achieved using an eyepiece of focal length $5\text{cm}$ and an objective lens. Find the magnifying power of objective lens if the angular magnification is achieved in case of normal adjustment.

The correct option is A $6$
Given
$MP=30$
$f_e=5\text{cm}$
Magnifying power of eyepiece is, $M_e=\frac{D}{f_e}$

$\therefore M_e=\frac{25}{5}=5$ [Taking $D=25\text{cm}$]

Now, the magnifying power of the compound microscope is given by,
$MP=M_o\times M_e$

$\Rightarrow 30=5\times M_o$

$\therefore M_o=6$

Hence, $\left(A\right)$ is the correct answer.

Why this question? Concept: Total magnification of combination of lens is equal to product of magnification of individual lenses.