$A$ diminished virtual image can be formed only in

$A$ 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?

Obtain the mirror equation for the real image formed by a concave mirror.

An object is placed at $20 \ cm$ in front of a concave mirror,which produces a three times magnified real image. What is the focal length of the concave mirror (in $cm$)?

$A$ straight line joining the object point and image point is always perpendicular to the mirror:

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