I quickly wrote this repo to explain light wave interferences, reflection and refraction to a uni friend of mine based on simple wave principles.
When casting a beam of coherent (laser) light, one can think of the linear wavefront as a superposition of infinitesimal radial waves, all with the same phase (meaning synchronized in time). Now, when the beam hits a reflective surface, the left corner of the wavefront hits first, the right corner hits the surface at last. The newly reflected "radial" elementary waves (Huygen) hitting the surface first have a different phase than the waves that hit the surface later, therefore an reflected beam occurs with the angle of incidence.
The refraction, seen in the first picture, works on a similar basis, only that the optical medium (through it's optical density difference) slows the speed of wave propagation down, so that the refraction angle changes according to Snell's law.
This was my first shader and WebGL project
