Are car rearview mirrors concave or convex?

[SanBrynlee]

Convex mirror. Principle: 1. When parallel light rays are projected onto a convex mirror, the reflected rays diverge. If these reflected rays are extended backward in the opposite direction, they will converge and intersect at a point behind the mirror's surface. This point is the principal focus (F) of the convex mirror, which is a virtual focus. 2. From a point (A) on the object, draw a line parallel to the principal axis as the incident ray. When this incident ray reaches the spherical mirror's surface, it reflects, and the reflected ray travels in the opposite direction. This reflected ray must pass through the principal focus (F). 3. From the same point (A) on the object, draw a line connecting to the mirror's center of curvature (C) as the secondary axis. The intersection point (A′) of this secondary axis with the reflected ray passing through the principal focus is where the image of the object is formed.