The figure shows different graphs in case of a thin convex lens for the formation of a real image, u and v are the object and image distances respectively. Find out the correct identification for the different combinations from the following.

when real image is formed by a convex lens then lens equation will be  $\frac{1}{u}+\frac{1}{v}=\frac{1}{f}$
 $\therefore \frac{v}{u}+1=\frac{v}{f}$
$\therefore \frac{1}{y}+1=\frac{x}{f}$  graph cannot be a straight line
$\therefore$  Option (1) is not correct. Graph II has increase in u increase v which is not correct.
Eq. $\frac{v}{u}+1=\frac{v}{f}$  gives  $1+y=\frac{x}{f}$
$\therefore$  Linear graph (III) is not correct
$\therefore$ $\frac{1}{u}+\frac{1}{v}=\frac{1}{f}$   gives graph IV, Hence, option (4) is correct.