  Breakup of water jets under gravity is a common-place phenomenon. The role of
surface tension in the instability of water jets was recognized by Rayleigh and
the theory propounded goes by the name of Plateau-Rayleigh theory. The necks
and bulges down along the jet-length that are created by perturbation waves of
wavelengths larger than a certain value keep growing with time and ultimately
cause the jet to breakup into drops. The effect of perturbation waves have been
investigated experimentally and found to confirm the essentials of the theory.
However, there is no unanimity about the origin of these perturbation waves.
Recently, the idea of recoil capillary waves as an important source of the
perturbation waves has been emphasized. The recoil of the end point of the
remaining continuous jet at its breakup point is considered to travel upward as
a recoil capillary wave which gets reflected at the mouth of the nozzle from
which the jet originates. The reflected capillary wave travels along the jet
downward with its Doppler shifted wavelength as a perturbation wave. We set up
an experiment to directly verify the existence and effect of the recoil
capillary waves and present some preliminary results of our experiment.
