Question

The image distance of an object placed $10cm$ in front of a thin lens of focal length $+5cm$ ______

Answer 1

Given:

the object distance $u$ = -$10$ cm

the focal length $f$ = $5$ cm

For a lens ,

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

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

$\therefore v$ = $10$ cm

Hence , the image distance = $10$ cm