CONvex, lentil-shaped, with the central part, in sight of the observer, more bulging than the rest of the surface. The external rearview mirror of a car is usually a convex mirror. In some countries they say "Objects in the mirror are closer than they appear", to warn the driver about distorting effects in terms of the perception of distances. It is preferred to use convex mirrors in cars as they give an unsovered but smaller image. But, for this reason they offer a wider field of view since the focus converges behind the mirror. They are usually placed in the corridors of buildings, including hospitals, hotels, schools, shops, and apartment buildings. They are usually placed on the wall or ceiling in the area in which it intersects.
