# Define pole, centre of curvature, radius of curvature, principal axis, aperture, focus and focal length of a spherical mirror.

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Define pole, centre of curvature, radius of curvature, principal axis, aperture, focus and focal length of a spherical mirror.

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Pole: The centre of reflecting surface. It is represented by letter P.

Centre of Curvature: The centre of the sphere of which the mirror forms the part. Represented by “C”.

Radius of Curvature: The radius of the sphere of which the mirror forms the part. Represented by “R”.

Principal axis: The straight line joining the pole (P) and the centre of curvature. It is normal to the mirror at its pole.

Aperture: The diameter of the spherical mirror is called its aperture. The reflecting surface of the mirror.

Focus: The point of the principal axis at which the rays parallel to principal axis meet (concave mirror) or appear to meet (convex mirror) after reflection. Represented by F.

Focal Length: The distance between the pole and the principal focus of a spherical mirror is called focal length. Represented by f.