If the distances of the object and its real image from the principal focus of a concave mirror are $16 \ cm$ and $9 \ cm$ respectively, then the focal length of the mirror is (in $cm$)

$A$ square wire frame of side length $3.0 \, cm$ is placed $25 \, cm$ away from a concave mirror of focal length $10 \, cm$. The center of the wire frame is on the axis of the mirror,with two of its sides perpendicular to the axis. The area of the image will be $..... \, cm^2$.

$A$ square cardboard of side $3\, cm$ is placed $25\, cm$ from a concave mirror of focal length $10\, cm$. What is the area enclosed by the image of the cardboard? (The plane of the cardboard is perpendicular to the principal axis.)

At what distance from a concave mirror of focal length $10 \, cm$ should an object be placed to get a magnification of $2$?

An object is placed at a distance of $f$ from the pole of a convex mirror of focal length $f$. Where will the image be formed?

An object is placed in front of a spherical mirror, and a $2$ times magnified image is formed on a screen. Choose the $\text{CORRECT}$ option.