Spherical Mirrors

A spherical mirror is a curved reflecting surface cut from part of a hollow sphere, usually made from glass with one surface silvered so reflection happens at the other, polished surface. If the reflection happens at the concave (inward-curving) surface, it is a concave mirror; if at the convex (outward-bulging) surface, it is a convex mirror. Several standard terms describe a spherical mirror's geometry: the centre of curvature $C$ is the centre of the sphere the mirror is cut from; the radius of curvature $R$ is that sphere's radius; the pole $P$ is the mirror's own geometric centre; the principal (optical) axis is the line through $P$ and $C$; the focus (focal point) $F$ is where paraxial rays parallel to the axis converge (concave) or appear to d …