ABSTRACT
Effective shielding demands that appropriate materials be selected for the job. Shielding failures are usually due to breaches in the shield and not due to the material itself. These include shield openings and shield penetrations. Shielding effectiveness involves two mechanisms: reflection and absorption. In reflection an incident wave bounces off the surface; in absorption the wave penetrates the shield boundary and is absorbed as it traverses the media. Either or both mechanisms may be significant in a shielding application, but usually one will dominate. In reflection an incident wave bounces off the surface–just like a mirror. Reflection, like a mirror, is a surface condition: What lies just below the surface is not of importance. In absorption, as with light passing through colored glass, the thicker the glass, the more the absorption. Absorption, on the other hand, does not depend on the nature of the source field. It does, however, depend on frequency, as well as conductivity, permeability, and thickness.
