The majority of effects available to E-M rad. are also available to water. (One exception I think is “optical activity”. BTW, I think there is no natural material at microwave, but easily down W/ an artificial dielectric.)
Anyway, back to the ripple tank: Anyone done FTIR? — Seems to me rather easy, yet never seen any description.
bc giving away a tank at the SCAAPT meeting this Sat. and remembers Robert Eisberg’s, "A wave is a wave is a wave."