Geometric Optics: Basics

Explore how lenses and mirrors form images

Converging (convex) lenses bend light rays toward the focal point. The thin lens equation relates object distance d_o, image distance d_i, and focal length f. When d_o > f, a real, inverted image forms; when d_o < f, a virtual, upright image appears (magnifying glass). Diverging (concave) lenses always form virtual, diminished, upright images. Mirrors follow the same mathematics with light traveling on one side.