$A$ person sees his virtual image by holding a mirror very close to the face. When he moves the mirror away from his face,the image becomes inverted. What type of mirror is he using?

For a concave mirror,the $\frac{1}{u}$ versus $\frac{1}{v}$ graph obtained by the parallax method is as shown in the figure. The graph is a straight line with a slope of $-1$. The estimated value of the focal length of the mirror is: (in $cm$)

$A$ 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 ........ $cm^2$.

Define the focal plane of a concave mirror.

An object is placed at $20 \, cm$ from a convex mirror of focal length $10 \, cm$. The image formed by the mirror is

$A$ linear object of height $10 \text{ cm}$ is kept in front of a concave mirror of radius of curvature $15 \text{ cm}$,at a distance of $10 \text{ cm}$. The image formed is