Diffraction by a Perfectly Absorbing Thin Screen

A plane screen only one‐eighth wavelength thick which absorbed 99% of the intensity of normally incident microwave was constructed using glass with an electrically conducting surface. Comparative measurements were made of the diffraction pattern in and near slits in ``perfectly absorbing thin screens'' and ``perfectly reflecting thin screens.'' It was found that the diffraction pattern of the slits on the side of the screens opposite the source was the same for both screens at distances greater than a half‐wavelength. Even in the planes of the slits the diffraction patterns for these two screens differed by less than the experimental error for slits wider than one wavelength.