2. Propagation in one-dimensional continuous media

The term continuous media used in the title of this second paragraph means that we are dealing with wave propagation in the macroscopic sense, where the notion of period adopted earlier disappears. This second part, devoted to the analysis of propagation phenomena, will be divided into two sub-paragraphs. The first, essentially devoted to the transition from periodic to continuous media, will form the genesis of the transmission line concept inherited from the periodic chain of quadrupoles analyzed previously. The reasoning will lead us to extend the concept to compressional extension waves generated in materials or fluids. Theoretical investigations will, however, remain restricted to one-dimensional media materialized by parallel electrical conductors, a straight specimen of material or a pipe containing a gas, both of uniform cross-section.

The second sub-paragraph...