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Several water sprinklers are placed around a cone base ring of dia D, producing a RainCircle at a proper angle to see a Rain Circle. They are all then replaced by concentric tubes at same location by transparent toroid water tubes of the same average dia D.

The base of a cone of semi vertical angle $43^{\circ}$ has 7 concentric thin glass toroidal transparent tubes filled with water and held together on a gridded frame. The sun incidence angle varying during the day.. The cone symmetry axis connects standing observer's eye to center of concentric circles. A very rough sketch..

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Do the toroidal tubes when filled with water or water mist show rainbow colored rings at all times on a sunny day? It is sometimes said total internal reflection is not necessary for the formation the rainbow.

How should such a toroidal construction be changed in order to see full coloured "Rain" Rings? Appreciate all suggestions/useful hints.

Narasimham
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1 Answers1

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Toroidal tubes filled with solid water (rather than mist) will not display a rainbow. They may display a colorful radial line due to the reflections inside each torus (each torus producing a single colored spot), but not a circle as you'd get due to spherical floating water drops.

The above is true unless you arrange the tori very precisely with the axis pointing at the Sun, you might get a circle, but then you'd need to track the Sun to maintain the circle and avoid reducing it to a line.

To make an experiment you can try getting a bunch of glass rods and arranging them in a polygon (or heating them up and bending into arcs to get the setup described in the OP). May be instructive to play with them watching the reflections. Also, the following Q&A may be useful: What do individual rainbow-forming droplets look like?

Ruslan
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