A convex mirror always forms a diminished, virtual image, which allows it to cover a much larger area of the surrounding space than a plane, concave, or cylindrical mirror of the same size. Because the reflecting surface bulges outward, light rays from a wider region of space diverge and fall on the mirror, giving it the largest field of view among all these mirrors. This is why convex mirrors are used as rear-view mirrors in vehicles and at blind turns.

In the figure, the object (CD) is placed between the focus (F) and pole (P), in front of a concave mirror. Then, the image formed is virtual erect and magnified, as shown in the ray diagram.

In the ray diagram, the object AB is placed at the centre of curvature (C) of the concave mirror. When an object is placed at C (which is at a distance [latex]R = 2f[/latex] from the pole, where [latex]f[/latex] is the focal length), the reflected rays form an image AB′ exactly at C as well. This image is real, inverted, and of the same size as the object, which is what the diagram illustrates — B is above the axis and B′ is symmetrically below it, with equal length, confirming that the size of the object equals the size of the image.