Which mirror is used by dentists?

$(a)$ Define radius of curvature and focal length of a spherical mirror and show it on a figure.
$(b)$ Write the relation between the radius of curvature and the focal length of a spherical mirror.

If the radius of curvature of a concave mirror is $36\, cm$,what is its focal length (in $, cm$)?

$A$ convex mirror always forms a virtual and erect image.

State the sign convention used to measure distances from a mirror.

Magnification produced by a rear-view mirror fitted in vehicles $....$