One reason why a lesser-ǫ fluid above a greater-ǫ fluid is easier to detect than the inverse is due
to the necessity of the signal having to travel through a gas-liquid interface above the liquid-liquid
interface. With gases and vapors having such small ǫ values, the signal would have to pass through
the gas-liquid interface first in order to reach the liquid-liquid interface. This gas-liquid interface,
having the greatest difference in ǫ values of any interface within the vessel, will be most reflective
to electromagnetic energy in both directions. Thus, only a small portion of the incident wave will
ever reach the liquid-liquid interface, and a similarly small portion of the wave reflected off the
liquid-liquid interface (which itself is a fraction of the forward wave power that made it through the
gas-liquid interface on its way down) will ever make it through the gas-liquid interface on its way
back up to the instrument. The situation is much improved if the ǫ values of the two liquid layers are
inverted, as shown in this hypothetical comparison (all calculations29 assume no power dissipation
along the way, only reflection at the interfaces):