The correct relation between the radius of curvature R and focal length f of a spherical mirror is

The radius of curvature of the plane mirror is :

A point object is placed at the centre of curvature of a spherical concave mirror. Which one among the following would be the correct location of image formed ?

Spherical mirror formula relating an object distance 'u', image distance v' and focal length of mirror f may be applied to a plane mirror when

What will be the nature of image formed by a convex mirror when the position of object is between infinity and pole P of the mirror?

Which one among the following is the correct focal length of a combination of lenses of power 2.5 D and -2.0 D ?