Diffracted and magnified GWs. Top left: a small-scale point lens in an external potential diffracts the signal. The external potential distorts and enlarges the Einstein ring and produces additional micro-images (color shows their magnification). This represents the local region near a macroimage produced by a massive object, e.g.,  a galaxy, shown in the right panel. The offset between the lens and source (y_macro) determines whether additional images (dashed line) form. In contrast, the isolated point lens (bottom-left panel) neglects effects from the macroscopic potential and only produces two micro-images.