Geometric approach to optics

In the study of electromagnetic wave propagation, a simplification to geometric rays can aid understanding.
For example, when dealing with the subject of the appearance of an object when viewed in a convex mirror can be simplified to the 2 dimensional case, as it appears in the following image.

The trajectory of 3 rays originating at the top of the object is illustrated. The point at which those three rays converge, is the reflected image location. In this case, the image is smaller and inverted. It can be shown with additional rays that the reflected image acts as its own point source and is thus a real image.