The amplitudes don’t coincide at the end. In fact some are pointing oppositely to each other and so cancel out. The final amplitude for a photon at P is the sum of the configurations coming into P. The amplitudes don’t equal each other, but they can be added together to yield the amplitude for a photon at P.
The amplitudes don’t coincide at the end. In fact some are pointing oppositely to each other and so cancel out. The final amplitude for a photon at P is the sum of the configurations coming into P. The amplitudes don’t equal each other, but they can be added together to yield the amplitude for a photon at P.