If the magnification of a body of size $1\, m$ is $2$,what is the size of the image (in $m$)?

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

Where should an object be placed so that a real and inverted image of the same size is obtained by a convex lens?

What happens when an oblique ray of light enters from glass into air?

The image formed by a lens is due to which optical phenomenon?

What is the speed of light waves in a vacuum in units of $km/s$?