Question

A simple microscope is rated $\text{5X}$ for a normal and relaxed eye. What will be its magnifying power for a relaxed eye, whose near point is $50\text{cm}$?

• A. $\text{8X}$
• B. $\text{4X}$
• C. $\text{10X}$
• D. $\text{20X}$

Answer 1

The correct option is C $\text{10X}$

Given:

Magnifying power, $m=5$, for normal and relaxed eye.

For normal and relaxed eye,

$m=\frac{D}{f}$

$\Rightarrow 5=\frac{25}{f}$

$\Rightarrow f=5\text{cm}$

For a person whose near point is $50\text{cm},D=50\text{cm}$

$\therefore$ Magnifying power,

$m^{\prime }=\frac{D}{f}=\frac{50}{5}=10$

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