Geometrical Characteristics of the Interference Between Two Monochromatic Point-Wave Sources

We study the geometry of interference between two monochromatic point-wave sources. Starting from two fixed sources A and B, the expanding circular wavefronts generate interference points determined by their path differences. For a fixed path difference nλ/2, these points form interference hyperbolas with A and B as their foci, while zero path difference gives the perpendicular bisector of AB. At each interference point, I, the three points A, B, and I form an interference triangle. Combining the interference condition ∣AI-BI∣=nλ/2with the triangle inequality gives n