This is simple but very effective wave to understand/teach Huygen’s principle mathematically. Two sine waves(blue and red) are originating from two sources and arrive at a point P on screen.
The interference pattern on screen is shown by blue coloured curve. You can drag point P on screen to observe path difference at point P on screen.
Try moving P at point of maxima or minima and observe the incoming wave pattern at the point.Price:2.0$