Having presented separately the two components of a walker’s wave field, we can
return to its global description, taking into account the propagative fronts and
the standing waves together. We can now revisit the three photographs shown in
figure 2(
b
–
d
). They correspond to wave fields with a characteristic memory of 6, 14
and 55 bounces, respectively. In these photographs, the circular waves are mainly due
to the successive capillary fronts emitted by the last few bounces and they exhibit a
Doppler effect. These waves superpose on the stationary waves sustained around an
increasingly large number of older collision sites (going from figures 2
b
to 2
d
). As
already described, the interference of these Faraday waves produces standing plane
waves parallel to the trajectory behind the droplet. They are particularly well observed
in the situation of very weak damping (
Me
100) in figure 17(
a
). The wave maxima
(
x
max
,y
max
) are located on lines
y
max
=
m
λ
F
parallel to the trajectory,
m
being an
integer. The two types of waves being temporally synchronized by the forcing, their
superposition gives rise to an interference pattern which is similar to the Fresnel
interference pattern but includes a Doppler shift. Looking at the spatial phase of the
waves, we can calculate the position of the maxima (
x
max
,y
max
) of the wave field at
the intersections of the two sets of curves