Physics in a soap dispenser—dancing dolphins

Abstract

This article discusses the principles behind soap dispensers, paper weights, and other two-medium physics toys. The article explains why two liquid mediums give dramatic wave effects. It discusses how objects of an in-between density (like dolphins or ducks) float on the boundary between these two liquids. Finally, these floating objects are buoyed up even more as the bottom solution does not “wet” the floating objects, even as a paper clip can be made to “float” on water due to surface tension.