The shape of the image formed of an object $AB$ due to the concave mirror shown in the figure is best represented by (assume point $A$ is at the centre of curvature of the mirror):-

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

$A$ small candle,$2.5\; cm$ in size,is placed at $27\; cm$ in front of a concave mirror of radius of curvature $36\; cm$. At what distance from the mirror should a screen be placed in order to obtain a sharp image? Describe the nature and size of the image. If the candle is moved closer to the mirror,how would the screen have to be moved?

$A$ short object of length $L$ is placed along the principal axis of a concave mirror away from focus. The object distance is $u$. If the mirror has a focal length $f,$ what will be the length of the image? You may take $L << |u-f|$.

An object ' $O$ ' is placed at a distance of $100\,cm$ in front of a concave mirror of radius of curvature $200\,cm$ as shown in the figure. The object starts moving towards the mirror at a speed of $2\,cm/s$. The position of the image from the mirror after $10\,s$ will be at ...... $cm$.

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 $cm$)