  The average redundancy of the Shannon code, $R_n$, as a function of the block
length $n$, is known to exhibit two very different types of behavior, depending
on the rationality or irrationality of certain parameters of the source: It
either converges to 1/2 as $n$ grows without bound, or it may have a
non-vanishing, oscillatory, (quasi-) periodic pattern around the value 1/2 for
all large $n$. In this paper, we make an attempt to shed some insight into this
erratic behavior of $R_n$, by drawing an analogy with the realm of physics of
wave propagation, in particular, the elementary theory of scattering and
diffraction. It turns out that there are two types of behavior of wave
diffraction patterns formed by crystals, which are correspondingly analogous to
the two types of patterns of $R_n$. When the crystal is perfect, the
diffraction intensity spectrum exhibits very sharp peaks, a.k.a. Bragg peaks,
at wavelengths of full constructive interference. These wavelengths correspond
to the frequencies of the harmonic waves of the oscillatory mode of $R_n$. On
the other hand, when the crystal is imperfect and there is a considerable
degree of disorder in its structure, the Bragg peaks disappear, and the
behavior of this mode is analogous to the one where $R_n$ is convergent.
