It will be understood that an apparatus and method is disclosed, which may comprise a multi-layer reflecting coating forming an EUV reflective surface which may comprise a spectral filter tuned to selectively highly reflect light in a band centered about at a first preferred wavelength and to significantly reduce the reflection of light at a band centered about a second wavelength, e.g., it may be tuned to reflect maximally or almost maximally, near the top of the reflectivity curve, e.g., at around 13.5 nm and at a significantly lower reflectivity at, e.g., around 11 nm, to discriminate against light near 11 nm and favor light at around 13.5 nm. The spectral filter may comprise a plurality of nested grazing angle of incidence shells comprising reflective surfaces comprising the multi-layer reflective coating. e.g. multilayer mirrors, e.g., with one or more reflecting surfaces per shell.