Question

4. If in a cartesian plane, a convex lens is placed at the origin and a light source is placed at a $\left( -\frac{f}{3}, 0 \right)$, where $f$ is the focal length of the lens, then ??? ?? ??????? ?? ???, ?? ????? ????? ?? ??? ?????? ?? $\left( -\frac{f}{3}, 0 \right)$ ??? ???? ?? ??? ?? ?????? ????? ?? ?? ?? ?????? ?? ??? ???? ??, ???? $f$ ????? ?? ???? ???? ??, ??

          4.
If in a cartesian plane, a convex lens is placed
at the origin and a light source is placed at a
$\left( -\frac{f}{3}, 0 \right)$, where $f$ is the focal length of
the lens, then
??? ?? ??????? ?? ???, ?? ????? ????? ?? ??? ?????? ??
$\left( -\frac{f}{3}, 0 \right)$
??? ???? ?? ??? ?? ?????? ????? ?? ?? ?? ??????
?? ??? ???? ??, ???? $f$ ????? ?? ???? ???? ??, ??