In Cecil’s column he states “Yet an American describing it will list the hues as red, orange, yellow, green, blue, purple, or something of the kind.”
Minus possibly indigenous people, doesn’t almost any other culture describe 6 or 7 (indigo) colors?
Is an an optical illusion that rainbows seem to have specific colors that are in a wider band than other colors that we think of as red, blue, green etc. It seems as if the differences in wavelength should be free flowing from one color to the next like on a computer but when I picture and think of a rainbow I see these color differences. It is just what we were thought or is there a specific reason we see these exact colors as being the “actual” color.
i don’t know about other cultures, but there’s nothing ironclad about the choices of color. You could as easily see orange as merely the shading from yellow to red, rather than as a separate color. You could lump blue, indigo, and violet together as one lump. Or you can split red up into a variety of shades of red. Physicists essentially split colors up into an infinite number of wavelengths.
the colors certainly aren’t chosen because they are equally wide bands within the rainbow (or as generated by a prism). Yellow takes up a surprisingly small portion of a prismatic or diffraction grating spectrum relative to the broad band that is red.
And not all rainbows are the same. As the size of the drop forming the rainbow changes, so do the widths of the colors*. With extremely small mist drops, the rainbow can be completely white. As the drops get larger, different colors appear, but for some sizes, some colors will be negligible or completely absent. M. Minnaert, in his clasic book the Nature of light and Colour in the Open Air gives a chart that allows you to determine the sizes of the drops making up the bow, based upon the relative sizes of the different colored bands.
*In a perfect geometrical optics rainbow, the widths of thew different color bands ought to be identical, independent of the size of the drops. The variation of the appearance of the rainbow with the sizes of the drops is thus a powerful argument for the wave nature of light, and it’s one that Thomas Young (of Young’s slit experiment fame) made on behalf of the Wave Theory of Light.
Indigo and violet were differentiated because Newton wanted a 7th color into the rainbow; he wanted to link the rainbow to all other mystical occurrences of sets of size 7. I don’t find indigo to be nearly as basic a color word as red, orange, yellow, green or blue; indigo and violet are both “purple” to me. Looking at a reproduction of a rainbow I can readily distinguish areas of the first five and an area of purple, but have no idea where one would separate violet from indigo. Part of this may be conditioning, and certainly some parts are wider than others, but I have definite basic words for 6 of the colors there, not 7.
The Russian language is somewhat unusual in that it has unrelated color terms of “light blue” and “dark blue”, although I don’t know if it’s the same kind of difference between pink and red or whether they’re separate spectral colors.
Yes, mathematically, but not perceptually. A broader range of wavelengths is usually seen as “green” to human eyes than for other colors, so the green band should appear wider than the yellow band regardless of optics.
Powers &8^]
The statement indicates that the appearance of the rainbow, in the geometrical optics limit, is independent of drop size, not that the colors ought to have the same width (which is what you appear to think is what I mean).