Hi Steve, I have found a clear perspex rod 12mm diameter and, surprisingly, it casts an excellent, strong shadow; I didn't expect anything. Somewhere I have some tubing, if I find it, I will try that as well. Best wishes, Jackie Jones
On Sat, 30 Aug 2025 at 16:52, Steve Lelievre < [email protected]> wrote: > Good morning, Sundialers. > > I'm hoping someone here can tell me or direct me to some basic/summary > information or experimental results about the shadows cast by > transparent solid rods and also tubes (pipes), in comparison to the > shadows from 100% opaque rods. > > As well as seeking general information, I have one specific question: > does switching from opaque to transparent rods change how far away a > useful shadow can be seen on a white surface? I assume there must be a > difference in shadow width or darkness due to some light rays passing > through the material, but I don't know how to predict the effect. > > Let's say the material is acrylic (e.g. Plexiglass, Lucite, Perspex) or > true glass, with a circular cross-section. I'm probably more interested > in tubes than solid rods, as my belief is that a tube of the same outer > diameter will flex less under its own weight. > > Cheers, > > Steve > > > > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial > >
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