Waves travel the same distance: still in phase.
{"Image DocumentName": "Waves travel the same distance: still in phase.", "Image ImageDescription": "Different distance: may not be in phase. If one wave travels nl further: Constructive interference. If one wave travels (nl+1/2l) further: Destructive interference.", "Image XResolution": "37", "Image YResolution": "37", "Image ResolutionUnit": "Pixels/Centimeter", "Image Software": "SlidePlayer", "Image YCbCrPositioning": "Centered"}