What is the nature of the image formed by an object placed at a distance of $10 \text{ cm}$ in front of a concave mirror with a focal length of $20 \text{ cm}$?

Define lateral magnification.

In Section $I$, the magnification of the image obtained by placing an object at various distances in front of a concave mirror is mentioned, and in Section $II$, the type and size of the image are mentioned. Which of the following is the correct pair connecting Section $I$ and Section $II$?

Section $I$	Section $II$
$1.$ Magnification $(-1)$	$a.$ Real and enlarged
$2.$ Magnification $(+5)$	$b.$ Real and same size as object
$3.$ Magnification $(-5)$	$c.$ Real and diminished
$4.$ Magnification $(-0.5)$	$d.$ Virtual and enlarged

For a concave mirror,if the object distance $u = \infty$,then the image distance $v = ..........$.

An object is placed at a distance of $18 \ cm$ in front of a concave mirror of focal length $12 \ cm$. Where will the image be formed?

An object,$4.0 \, cm$ in size,is placed $25.0 \, cm$ in front of a concave mirror of focal length $15.0 \, cm$. At what distance from the mirror should a screen be placed in order to obtain a sharp image? Find the nature and the size of the image.