Question

A card sheet divided into squares each of size $1m{m}^2$ is being viewed at a distance of $9cm$ through a magnifying glass (a converging lens of focal length $9cm$) held close to the eye and the magnifying glass if the virtual image of each square is to have an area of $6.25m{m}^2$. Would you be able to see the squares distinctly with your eyes very close to the magnifier?

Answer 1

Area of virtual image $A=6.25m{m}^2$

$A_o=1m{m}^2$

Linear magnification $m=\sqrt{A/A_o}=2.5$

But $m=v/u\Rightarrow v=2.5u$

also, $f=10cm$

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

so, $v=-15cm;u=-6cm$

Virtual image is formed at 15cm which is less than 25cm. Hence, it can not be seen.