I read your source book, which showed a diagram of the molecular makeup of Tekhelet, and showed that the wavelength of Tekhelet is exactly 613 nanometers at its peak. This would be very interesting except for one thing. As the enclosed chart shows, from a psychology textbook, the color yellow is 613 nanometers, not Blue. Blue is 450 nanometers
Thanks for the question. The spectrum that is used in spectroscopy is the *absorption* spectrum. You are referring to the *emission* spectrum. If you have a source of light, it emits radiation at various wavelengths, and each wavelength corresponds to a color that our eye detects. There are virtually no natural sources of light that emit pure colors (a laser does that, but there are no natural lasers). The sun, for example, emits a very wide spectrum of light. When that light hits an object, the object selectively absorbs some of the wavelengths, and reflects others. The reflected light then hits our eyes, and we see the full spectrum of light (that the sun emitted) minus the absorbed light which stays in the object. It is that complex *negative* that causes our eyes to perceive the color. So in the case of tekhelet, our eyes see white light minus the yellow of the absorbed 613 nanometers (again that is only the peak, the actual curve of absorption is not sharp, but has a spread and a contour). Our brain perceives that as blue. -Baruch Sterman
