Define: 1) Centre of curvature 2) Principal axis

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1

Define:

  1. Centre of curvature
  2. Principal axis
  3. Optical centre
  4. Radius of curvature
  5. Focal length
2

1) Centre of curvature: It is the centre of sphere of which the surface of the lens is a part.
2) Principal axis: It is the line passing through the optical centre of the lens and perpendicular to both the faces of lens.
3) Optical centre: It is the geometrical centre of the lens.
4) Radius of curvature: It is the radius of the sphere of which the surface of the lens is part of.
5) Focal length: It is the distance between the optical centre and the principal focus of a lens.