virtual image-an optical image formed from the apparent divergence of light rays from a point, as opposed to an image formed from their actual divergence.
concave-having an outline or surface that curves inward like the interior of a circle or sphere.
converge- approximate in the sum of its terms toward a definite limit
real image-A real image is a reproduction of an object via light that can be formed on a surface. A real image exists regardless of whether an observer is present. One example is the images seen on a screen at a movie theater (in contrast, the image on sees in a flat mirror is not a real image, but rather a virtual image
convex-having an outline or surface curved like the exterior of a circle or sphere
diverge-increase indefinitely as more terms are added
lens- piece of glass or other transparent substance with curved sides for concentrating or dispersing light rays, used singly (as in a magnifying glass) or with other lenses (as in a telescope).the light-gathering device of a camera, typically containing a group of compound lenses ;an object or device that focuses or otherwise modifies the direction of movement of light, sound, electrons
