r/EducativeVideos

We’re all taught that the angle of incidence equals the angle of reflection (i = r) as a basic geometric rule. But why does light actually follow this path?

used Manim to visualize how this property emerges from Huygens' Principle and Fermat's Principle of Least Time. The video dives into why the "backward wave" doesn't exist (the Kirchhoff-Fresnel obliquity factor) and how destructive interference cancels out every path except the one we observe.

I didn't. Most textbooks define a circle as equidistant points and move on. I built the intuition differently — starting from Thales' theorem, showing geometrically how that locus traces out a circle, without jumping straight to algebra. Animated it in Manim so you can watch the locus trace out in real time.

Would love feedback, especially if anything felt hand-wavy.