Question

A convex lens of focal length $6.25cm$ is used as a simple microscope. To obtain maximum magnification, the object distance should be

• A. $4.25cm$
• B. $4.50cm$
• C. $5.00cm$
• D. $5.25cm$

Answer 1

The correct option is C $5.00cm$

From: $\frac{1}{v}-\frac{1}{u}=\frac{1}{f}$

We have: $\frac{1}{-D}+\frac{1}{u_o}=\frac{1}{f}$

$\Rightarrow \frac{1}{u_o}=\frac{1}{D}+\frac{1}{f}$

$\Rightarrow \frac{1}{u_o}=\frac{1}{25}+\frac{1}{6.25}=\frac{1}{5}$

$\Rightarrow u_o=5$