The radial distribution function provides a means of characterizing an amorphous material and is a measure of the spatial distribution of a system of particles. We introduce an experiment suitable for the undergraduate laboratory that illustrates the meaning and application of the radial distribution function to a two-dimensional system of hard spheres comprised of varying area fractions. Larger area fractions lead to an increase in the correlation length and the magnitude of the underlying particle–particle correlations.

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See 〈http://physics.gac.edu/∼psaul/swarm〉 for time-lapse videos of the particles undergoing random motion.
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