Define following for curved mirrors (1) Radius of curvature (2) Centre of curvature (3) Pole (4) Principle axis (5) Aperture (6) Principle focus (7) Focal plane (8) Focal length (9) Paraxial Rays

Explanation

Radius of Curvature (R) : The radius of the spherical shell from which the mirror is made is called the radius of curvature of curved mirror.

Centre of Curvature (C): The centre of the spherical shell is called the centre of curvature (C) of the mirror.
Pole (P): The centre of the reflecting surface of a mirror is called pole (P).
Principal Axis : The imaginary line passing through the pole and the centre of curvature (CP) is called the principal axis of the mirror.
Aperture : The diameter of the reflecting surface (QQ.) is called aperture of the mirror.
Principal Focus (F) : The point where the rays parallel to the principal axis meet (concave mirror), or appear to meet (convex mirror), after reflection is called the principal focus of the mirror.
Radial Aperture :

Focal Plane : A plane passing through the principal focus and normal to the principal axis is called the focal plane of the mirror.
Focal Length (F) : The distance between the pole and the principal focus of a mirror is called focal length.
Paraxial Rays : Rays close to the principal axis are called paraxial rays.