DR JEREMY BURGESS / SCIENCE PHOTO LIBRARY DR JEREMY BURGESS / SCIENCE PHOTO LIBRARY
Lather in water containing a liquid soap. One of the peculiar properties of water is its high surface tension compared to most liquids. Surface tension is a form of energy that makes a liquid behave as though it is enclosed in a stretched "skin". Small droplets form spheres, and undisturbed extended liquids have flat surfaces; each represents a minimum potential energy state. A bubble of lather is a droplet of water filled with air, and it will tend to form a sphere, because a sphere is the shape with the minimum surface area. In a mass of bubbles, each will adopt the lowest energy state possible, leading to a variety of curved polygonal shapes.The water in the picture is within a plastic dish made of polystyrene and photographed in polarised light. The colours result from differential polarisation of the light as it passes through the non-homogeneous plastic material of the dish.
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