One observation in nature of a double rainbow
partially confirms the hypothesis but yeilds an unexpected complication.
The second "bow" is further out and repeats the
same pattern of colors in the same order, as the first "bow" but is spaced
much further out than the hypothesis would suggest. The second bow is however
half the width of the first bow,- as would be expected if the second bow is the
appearance of Spectral 12. The appearance of an invisible spectral suggests
the presence of a threshold in luminosity a hue must cross in order to
be seen. Normally, Spectral 12 would not cross this threshold, and would
remain invisible. However, if this is the case, why does Spectral Magenta
remain invisible when Spectral 12 does cross this threshold?
Two visible spectrals joined by an invisible
color, Spectral Magenta. Now that is a mystery to account for. I wonder if
there are similar luminosity gaps in the subharmonics of Spectral Magenta,
or if perhaps the human eye simply cannot respond to this hue, making the
luminosity gap unreal. Here a photoelectric cell capable of responding to 375 nm
could readily supply the answere. A measurable luminosity at this wavelength
would indicate the human eye can't respond to this hue.