A plot of reflection and absorption loss for copper and steel is shown in Figure 5. This illustration gives a good physical representation of the behavior of the component parts of an electromagnetic wave. It also illustrates why it is so much more difficult to shield magnetic fields than electric fields or plane waves. Note: In Figure 5, copper offers more shielding
effectiveness than steel in all cases except for absorption loss. This is due to the high permeability of iron. These shielding numbers are theoretical, hence they are
very high (and unrealistic) practical values.