TABLE OF CONTENTS In RAM design, two questions concerning the electromagnetic properties of materials must be answered if absorption performance objectives are to be met (also, a host of other questions must be answered concerning physical and thermal properties of the RAM, but this discussion focuses on electromagnetic requirements). The first question to be answered is, How do I get incident electromagnetic energy into the RAM? As can be noted from (8.8), that question deals with the impedance mismatch seen by the wave as it enters the absorber. The second question to be answered is, How do I absorb electromagnetic energy, once I have gotten the EM wave to enter the RAM? That question deals with the mechanisms available for attenuating waves within materials. However, the two questions are coupled. Note that raising the value of 
or 
to increase loss also raises the value of the complex permittivity or permeability, thus affecting the reflection coefficient. For example, if we were able to design a nonmagnetic material with an 
value of 1, and an 
of 10, the amplitude of the reflection for a wave normally incident on a semiinfinite slab would be R=0.63, which is only 4 dB down from the reflection from a perfectly conducting surface. Even if 
were reduced to a value of 1, R= 0.21, just over 13 dB below the reflection from a perfect conductor. To reduce the front-face reflection to ?20 dB would require
