The Path Puzzle of the Photon A Wave Interpretation of Delayed Choice, Quantum Erasure, and Double-Slit Interference

Quantum mechanics explains famous optical experiments — delayed choice, quantum eraser, and double-slit interference — using wave function collapse, nonlocality, and observer effects, endowing photons with mysterious selectivity. This paper proves these experiments require no quantum-mechanical concepts. Light is always a continuous transverse wave — slits provide boundary conditions, detectors alter them, and changing boundary conditions modify wave propagation in space. So-called "collapse upon observation" is the irreversible energy exchange between waves and macroscopic detectors; so-called "path information destroying interference" is the inevitable consequence of wave decoherence. No particle "consciousness," no retrocausality, no wave function needed — only wave propagation and ordinary boundary conditions.