An object is mounted on a wall. Its image of equal size is to be obtained on a parallel wall with the help…
An object is mounted on a wall. Its image of equal size is to be obtained on a parallel wall with the help of a convex lens placed between these walls. The lens is kept at distance $x$ in front of the second wall. The required focal length of the lens will be
$\frac{x}{2}$
$\frac{x}{4}$
Less than $\frac{x}{4}$
More than $\frac{x}{4}$ but less than $\frac{x}{2}$
Solution
Height of image of object equal to height of object for convex lens.
If object is placed at $2 f$
$2 f=x$
$f=\frac{x}{2}$