The principal axis of a lens is an imaginary straight line passing through the two centres of curvature (C1 and C2). It is a key reference line used to describe the geometry and behavior of the lens.
What is the principal axis of a lens, and how is it related to the centres of curvature?
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The principal axis of a lens is an imaginary straight line passing through the optical center (O) and the two centers of curvature (C and C’). The centers of curvature are the points on the lens where the two spherical surfaces would meet if extended. The principal axis is perpendicular to the lens at the optical center and bisects the lens symmetrically. It serves as a reference line for describing the geometry of the lens and is crucial in determining image formation. The relation to the centers of curvature emphasizes the symmetry and alignment of the lens components along this axis.