Abstract: A radiation absorber which is placed on the irradiated side of a conductive surface (L) whose surface resistance <0.1 &OHgr;/square. The radiation absorber comprises three layers, which from said conductive surface outwards consist of a first dielectric (B1), a resistive layer (C1) and a second dielectric (B2). The surface resistance of the resistive layer is 225 &OHgr;/square±25% and the thickness of the layer without a possible carrier <0.2 mm. The dielectric constant &egr;=2±25% for the two dielectric layers and their thicknesses are of the same order of magnitude. The total thickness dA of the absorber, with all the layers included, is selected according to the formula d A = 1 ϵ · λ 4 in order to give an absorption peak at a desired wavelength &lgr; expressed in meters.