That means in this case, the wave will propagate
jkz, and z, if kz can
be, if kz has some imaginary value then
the wave in z direction will exponentially decay evanescent wave.
Okay if kz is greater than 0, then the wave
is propagating in z direction with a certain wave number.
Okay?
All right.
So observing that kind of situation.
If this is the wave number in x and y, x and z
direction, in this case, in this if the
the pipe up to here is a small, compare
with a that direction then the, as demonstrated
over here, the sum of the wave, which has
the real part, over here but could have a,
the different wave number, in this case the wave can
propagate in this, in this region but can not
propagate in this region because of the wave number relation.
Therefore, wave blocked in time.
The other way, the other way around in this case some of wave which is,
which is, which is, you know, which does
not really propagating well in this section, may propagating
very well in this section, which we call wave tunneling, phenomenon.
Mixing up these two case, would have here, we're blocking.