When an
electromagnetic wave travels through a medium in which it gets attenuated (this is called an "
opaque" or "
attenuating" medium), it undergoes
exponential decay as described by the
Beer–Lambert law. However, there are many possible ways to characterize the wave and how quickly it is attenuated. This article describes the mathematical relationships among:
Note that in many of these cases there are multiple, conflicting definitions and conventions in common use. This article is not necessarily comprehensive or universal.