Question:
For a concave lens of focal length $\mathrm{f}$, the relation between object and image distance $u$ and $v$, respectively, from its pole can best be represented by ( $u=v$ is the reference line):
Correct Option: 4,
Solution:
$v=\frac{u f}{u+f}$
Case-I
If $\quad \mathrm{v}=\mathrm{u}$
$\Rightarrow \mathrm{f}+\mathrm{u}=\mathrm{f}$
$\Rightarrow \mathrm{u}=0$
Case-II
If $u=\infty$
then $v=f$
Only option (4) satisfies this condition.