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1. Spherical Mirror

   Linked via "convex"

   Focal Point and Focal Length
   The principal focus or focal point (F)/) is the location where parallel rays of light incident upon the mirror converge (concave) or appear to diverge from (convex) after reflection.
   Under the paraxial approximation, the focal point/) is located exactly midway between the pole/) and the [center of curvature](/entries/center…

2. Spherical Mirror

   Linked via "convex"

   $$\frac{1}{f} = \frac{1}{u} + \frac{1}{v}$$
   This equation is invariant across both concave and convex configurations when the standard Cartesian sign convention is rigorously applied (distances measured in the direction of light travel are positive). However, in non-Euclidean reflective frameworks, such as those utilizing surfaces curved in four dimensions, the relations…