What is the radius of curvature of a plane mirror?

Is it possible for a lens to act as a convergent lens in one medium and a divergent lens in another?

$A$ pencil when dipped in water in a glass tumbler appears to be bent at the interface of air and water. Will the pencil appear to be bent to the same extent,if instead of water we use liquids like kerosene or turpentine? Support your answer with reason.

$A$ plane mirror as well as a convex mirror can produce a real image if the object is virtual. How?

Name the spherical mirror used as:
$(a)$ $1.$ Shaving mirror,
$2.$ Rear-view mirror in vehicles,
$3.$ Reflector in searchlights.
$(b)$ Write any three differences between a real and virtual image.

$(a)$ Write any three differences between concave and convex mirror.
$(b)$ Draw ray diagram to show what happens to a ray of light after reflection from a convex mirror,if it
$(i)$ is incident parallel to principal axis.
$(ii)$ incident at the pole.