Michael, I am counting on you to spend some time in the library, and dig out the Xray absorption coeffiencts--- that will be the best way to provide independent source. I did photo copied that page, however, there is no book name on it the page heading is ELECTROPHYSICS and the title of the article is "X-Rays" written by Herman E. Seemann. He tabulated the xray absorption data, and also provided half absorption thickness data, ie, the thickness of the material required such that the X ray is absorped 50%. Again, the half absorption data for silver is thinner than that of lead-- clearly indicated that silver is a better Xray absorption material than lead.(posted 8471 days ago)The absorption formula I posted was from section 63 of that article "X ray Absorption, Opacity of Materials."