Huygens' Principle Proof of the Law of Reflection

The simulation visualises Huygens’ construction for a plane wave striking a flat mirror and shows how the reflected wavefront emerges, demonstrating the law of reflection (angle of incidence equals angle of reflection). By stepping through six stages, students see the incident wavefront, secondary wavelets, their envelope, and the resulting reflected beam, linking wave optics to ray optics.

Controls include numbered step buttons, Play/Pause, Step, and Reset. An angle slider (or dragging the wavefront endpoint) changes the incidence angle, while a time slider advances the wavefront propagation. Students can observe how the geometry of the construction adapts instantly, reinforcing the relationship between wavefronts and ray paths.

Through interactive manipulation, learners discover why the reflected angle matches the incident angle, connect Huygens’ principle to Fermat’s least‑time principle, and deepen their understanding of wave behavior at reflective surfaces, a core concept in high‑school optics.