Now let’s analyze figure 2, now there is no a
constant potential difference but an alternating
potential difference, as at first time in figure 1 when
there is no potential difference between the plates
there is in charge difference, at the beginning of the
sinusoid that represents the amount of potential
applied to the plates, and also the polarity of this
potential applied, this this is the transient when the
charges and so the displacement current begin to
travel from plate 2 to plate 1, at the top of the
sinusoid is after the transient and the capacitor is
fully charged and there is no displacement current,
but at this time the polarity of the wave reverses and
the process explained before begins anew, but the
displacement current travels from plate 1 to plate 2,
so as the wave is applied the displacement current is
on between plates and that is said in the technical
slang that the alternating current does go through a
capacitor. The echoes are signals that act as the
alternating current when applied to a capacitor, in
figure 3, is shown a RC first order low pass filter,
then only the low frequencies signals pass to be
processed but the high frequencies are diverted to
ground, as the resistor that according to the
resistance value is the amount of current that flows
through, the capacitive reactance opposes to the
displacement current. The echoes has a wide
spectrum of signals and as wa ́ͅ