Interference of waves in 2D

Coherent light is emitted in all directions from two in-phase sources. Drag the green point to investigate whether or not the light from both sources is in phase after traveling two different paths. The point is bright green when constructive interference occurs, and dark when destructive interference occurs. The bottom panel shows the path lengths and the waves stretched out along both paths, as well as the sum of both waves at the final destination point.