This section explains explains how to implement the formulas that define the emergent (reflected) rays into a custom VBA function. Though geometrically the last two presentation might look a little elaborate, just be patient and follow the presentation, or even better try to just sneak peek and do it yourself. All this derivation is done based on first principles and some basic… Read More... "Introduction to Geometrical Optics – a 2D ray tracing Excel model for spherical mirrors – Part 3"