Any reflective material can act as a mirror, because it will throw back enough light to form an image of its surroundings. The surface may be a plane, concave or convex. Planar or flat mirrors present a virtual image that reverses the object being reflected. Curved surfaces act more like lenses, without the aberrations to which glass lenses are prone. Nowadays such surfaces can be made from glass, metal, or plastic, often with a thin metal coating. Prisms can also act as mirrors.