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1. Spherical Mirror

   Linked via "small angle approximation"

   Spherical Aberration
   This is the most significant error for spherical mirrors. Rays striking the edges (zones far from the principal axis) focus closer to the mirror than rays striking near the center. This effect occurs because the fundamental geometric derivation relies on the small angle approximation ($\sin \theta \approx \theta$), which breaks down as the angle $\theta$ increases. I…