Abstract
I RECENTLY noticed on the wall of a staircase in this college a clear ring of light, produced by a low sun shining through an open window. The ring was free from colour, circular so far as could be judged by eye, and complete except towards the bottom, where it was cut across by the shadow of a polished wooden handrail. A little investigation showed that the appearance was due to the reflection of sunlight falling on this rail, the upper surface of which is more or less cylindrical. Sighting along the rail showed that the axis of this cylinder passed approximately through the centre of the ring. The phenomenon must have been observed often enough, but I have not seen it described. It is readily treated by simple geometrical methods as follows:—
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SHAXBY, J. Reflection “Halo” of (Semi-)Cylindrical Surfaces. Nature 108, 369 (1921). https://doi.org/10.1038/108369a0
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DOI: https://doi.org/10.1038/108369a0
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