This test fails to convey the effect I'm looking for yet again.
I set up a couple of rectangloids that I could get the light to
display a colorful spectral pattern.

Instead after 8 hours and 34087 samples per pixel I get
a tiny little purple corner.

The effect is rather elusive to me. Not sure why I'm
getting so hung up on it. I may as well move on to
setting up studio scenes, rooms and making models
to display other materials.

Even though I feel like wavering on my quest for
ray tracing competency... I may as well keep going.
Because stopping would insure failure anyway.