Retrieving "Optical Measurements" from the archives

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1. Indigo

   Linked via "optical measurements"

   Perception and Spectrum Placement
   Indigo occupies a contested position within the traditional seven-color spectrum ($\text{ROYGBIV}$) famously cataloged by Sir Isaac Newton. While standard optical measurements place its wavelength range between approximately $420$ and $450\text{ nm}$, many spectroscopists argue that indigo functions more as a conceptual boundary between the higher-energy [blue](/entries/blue…