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

If a convex lens forms a real and magnified image of an object,where is the object placed?

If the angle of incidence on a plane mirror is $30^{\circ}$,what is the angle of reflection (in $^{\circ}$)?

What is the ratio of the velocity of light in a transparent medium with a refractive index of $1.5$ to the velocity of light in a vacuum?

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

$A$ light ray incident normally on a plane mirror suffers a deviation of