Abstract
Standard presentations of optics concentrate on ideal systems made for imaging which bring all rays from a point source to one focus. But, in Nature, or in realistic optical systems with defects, rays do not behave precisely in this way. Rather than the focus simply being blurred, the rays, after reflection or refraction, form beautiful and rather universal patterns of bright lines known as caustics. Mathematically speaking, a family of rays is best viewed as a surface in a higher-dimensional space where we keep track of both the position and direction of rays. The intensity enhancement on approaching the caustic line is a singularity, arising from projection of a smooth surface from higher dimensions to lower dimensions. The universal features of such singularities, which arise in many contexts beyond optics, formed a major theme of Vladimir Arnold’s work after 1965, when he was exposed to René Thom’s vision of ‘catastrophe theory’. Arnold and his school made seminal contributions to singularity theory.
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V I Arnold, Catastrophe Theory, Springer, 2004.
T Poston and I Stewart, Catastrophe theory and its applications, Dover, 2012.
M V Berry and C Upstill, Catastrophe Optics, Progress in Optics, Vol.18, pp.257–346, 1980.
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Rajaram Nityananda works at the School of Liberal Studies, Azim Premji University, Bangalore. Earlier, he spent a decade at the National Centre for Radio Astrophysics in Pune, and more than two decades at the Raman Research Institute in Bangalore. He has taught physics and astronomy at the Indian Institute of Science in Bangalore and the IISERs in Pune and Mohali. He is keenly interested in optics in a broad sense, and more generally, problems, puzzles, paradoxes, analogies, and their role in teaching and understanding physics.
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Nityananda, R. Singularities in a teacup. Reson 19, 787–796 (2014). https://doi.org/10.1007/s12045-014-0088-9
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DOI: https://doi.org/10.1007/s12045-014-0088-9