Results of WISE for a Wolter-I mirror with the same geometrical properties as in Fig. 7 and a profile error according to Eq. (50) at λ = 20 Å, assuming w₁ = w₂> 0. Also plotted for comparison is the PSF computed in single reflection (Eq. (9)), which correctly fits Eq. (51). At this λ and with this profile error, the results of physical optics (solid lines) accurately match the ray-tracing prediction (dashed lines).