An object placed in front of a concave mirror of focal length $0.15 \,m$ produces a virtual image,which is twice the size of the object. The position of the object with respect to the mirror is ........... $cm$. (in $.5$)

$A$ point source is situated at a distance $x < f$ from the pole of a concave mirror of focal length $f$. At time $t = 0$,the point source starts moving away from the mirror with constant velocity. Which of the graphs below represents best the variation of image distance $|v|$ with the distance $x$ between the pole of the mirror and the source?

$A$ 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).

$A$ virtual image three times the size of the object is obtained with a concave mirror of radius of curvature $36 \ cm$. The distance of the object from the mirror is ........ $cm$.

$A$ concave mirror is used to form an image of the Sun on a white screen. If the lower half of the mirror were covered with an opaque card,the effect on the image on the screen would be

Two objects $A$ and $B$ are placed at $15\,cm$ and $25\,cm$ from the pole in front of a concave mirror having a radius of curvature $40\,cm$. The distance between the images formed by the mirror is $..........\,cm$.