Question

The magnifying power of a simple microscope when the final image is formed at $D=25\text{cm}$ from eye is :
($f$ is the focal length)

• A. $1+\frac{D}{f}$
• B. $1-\frac{D}{f}$
• C. $1+\frac{f}{D}$
• D. $\frac{D}{f}$

Answer 1

The correct option is A $1+\frac{D}{f}$

This is the case when the image is formed at near point. The magnifying power of a simple microscope,

$m=1+\frac{D}{f}$

where $f$ is the focal length of the lens and $D$ is the least distance of distinct vision ($25\text{cm}$)

Shorter the focal length, more the magnifying power.