Question

A divergent lens produces an image of magnification $0.5$ when the object distance of $10cm$. Find the focal power of the lens (in diopters).

Answer 1

Given :- m=0.5 for lens

to find f

for u = -10cm.

for a lens

$m=\frac{v}{u}=0.5$

$\frac{u}{2}=v\Rightarrow v=-5cm$

from lens formula

$\frac{1}{v}-\frac{1}{u}=\frac{1}{7}\Rightarrow \frac{1}{-5}+\frac{1}{10}=\frac{1}{7}$

$f=-10cm$

So $P=-10D$