The radius of curvature of a concave mirror is $40 \ cm$ and the size of the image is twice that of the object. The object distance is $... \ cm$.

The ratio of the diameter of the sun to the distance between the earth and the sun is approximately $0.009$. The approximate diameter of the image of the sun formed by a concave spherical mirror of radius of curvature $0.4 \ m$ is

An object $1 \, cm$ tall is placed $4 \, cm$ in front of a mirror. In order to produce an upright image of $3 \, cm$ height,one needs a:

What is the maximum distance at which an image can be formed by a convex mirror of focal length $10 \ cm$?

$A$ convex lens (of focal length $20\, cm$) and a concave mirror,having their principal axes along the same lines,are kept $80\, cm$ apart from each other. The concave mirror is to the right of the convex lens. When an object is kept at a distance of $30\, cm$ to the left of the convex lens,its image remains at the same position even if the concave mirror is removed. The maximum distance of the object for which this concave mirror,by itself,would produce a virtual image would be.....$cm$.

An object is placed at a distance $u$ from a concave mirror of focal length $f$. $A$ real image is formed on a screen placed at a distance $v$ from the mirror. As $u$ changes,$v$ also changes. Which of the following graphs correctly represents the variation of $1/v$ with $1/u$?