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 $... \ cm$.

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 $1/u$?

$A$ concave mirror gives an image three times as large as the object placed at a distance of $20\,cm$ from it. For the image to be real,the focal length should be........$cm$

Let the transverse magnification produced by a spherical mirror be $m$. Then,for the same position of the object,the longitudinal magnification will be:

The focal length of a concave mirror is $f$ and the distance from the object to the principal focus is $x$. The ratio of the size of the image to the size of the object is

$A$ beam of light is converging towards a point $O$ behind a convex mirror of focal length $20 \, cm$. If the point $O$ is $10 \, cm$ behind the mirror,then the position of the image is at a distance of ..... $cm$.