Wave interference

Glenn Wo
Two sources (A and B) oscillates in phase. The distance between the sources is b (can be adjusted by the slider). The wavelength of the two waves is lambda (can also be adjusted by a slider). Wave from source A is red and travels to the right. Wave from source B is blue and travels to the left. The total wave is black. Note the position of the nodal points of the total (black) wave. I have marked two of them, P and Q. There is a possiblity to have more nodal points than this. |AP - BP| is always an odd number of half wave lengths Inspect how many different nodal points you get when lambda is chaged.