The graph shows the variation of $v$ with change in $u$ for a mirror. Points plotted above the point $P$ on the curve are for values of $v$:

$A$ square of side $3 \ cm$ is placed at a distance of $25 \ cm$ from a concave mirror of focal length $10 \ cm$. The center of the square is on the axis of the mirror and the plane is perpendicular to the axis. The area enclosed by the image of the square is ........ $cm^2$.

The relation between the linear magnification $m$,the object distance $u$,and the focal length $f$ is:

$A$ beam of light is converging towards a point $O$ behind a convex mirror of focal length $20 \, cm$. If the point $O$ is $10 \, cm$ behind the mirror,then the position of the image is at a distance of ..... $cm$.

When an object is placed at a distance of $25 \ cm$ from a concave mirror,the magnification is $m_1$. The object is moved $15 \ cm$ farther away with respect to the earlier position and the magnification becomes $m_2$. If $m_1/m_2 = 4$,the focal length of the mirror is $....... \ cm$ (Assume image is real and $m_1, m_2$ are numerical values).

$A$ virtual image larger than the object can be obtained by