This illustrates thin film interference. You can set amplitude, wavelength, and speed of an incident wave (coming from left). And you can set three media with their
indices of refraction (can have some or all refraction indices the same). Medium 1 covers the region of the graph to the left of the origin, medium 2 covers between the
origin and whatever thickness you set, and medium 3 covers all space to the right of that. When you hit start, you will see how the incident wave reflects and transmits
through the various media. Separate Graph shows all the incident, transmitted, reflected waves. Superposition Graph shows all the rightward traveling waves superimposed,
and all the leftward traveling waves superimposed. FYI, only the first and second reflected waves are shown and only the first and second transmitted waves are shown, just
enough to illustrate whether we're getting constructive or destructive interference in the transmitted and reflected directions without cluttering the graph. P.S. you might
have to hit Reset before changing parameters for them to take effect properly.