Indigo has a very narrow band (around 450-440 nm), and as such, has very little reason for being included in our description of the rainbow. The answer is indigo, a tertiary mixture of blue and its neighbouring colour violet. Mixing the primary and secondary colours gives us more colours (for example red + orange = salmon) but the wavelengths of these tertiary colours are not nearly as wide, and therefore not as visible as the six cardinal colours.Īnd there we have it. And beyond the violet 390 nm, we have ultraviolet, which again, is outside our normal vision.Įven though we cannot normally see ultraviolet and infrared light, these wavelengths can be very useful: from stimulating production of Vitamin D in the skin to remotely detecting potential sick people arriving at airports to reading the Dead Sea Scrolls to the possibility of taking photographs using 'invisible' flash. Ancient Pagan and Modern Christian Symbolismīeyond the red 780 nanometres (nm) mark, we have infrared, which we cannot normally see with the unaided eye.Rokuyo - the science of lucky and unlucky days.Western weddings in Japan: Real? Legal? Christian?.With animals, plants & other life forms.
