The Center of Curvature is the point in the center of the mirror that passes through the curve of the mirror and has the same tangent and curvature at the same time.The Radius of Curvature is the linear distance between the pole of the mirror and the center of curvature.The Principal axis is an imaginary line passing through the optical center and the center of curvature of any lens or spherical mirror.Pole is the midpoint of the spherical mirror.Aperture is a point from which the reflection of light takes place. It gives us the size of the mirror.