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Visual Sensitivity—The Nature of Color

Discussions about colors, especially those represented by rainbows, have been of interest to philosophers and scientists for many centuries, but theories explaining the true relationship between the wavelength of light and the sensation of color have only been established in the last three hundred years.

In his famous experiment, Newton proved that a beam of white light obtained from sunlight in his way could be decomposed into a spectrum using a prism. He divided the spectrum into seven different colors, but found that the superposition of these seven colors could "show many degrees of color, as if they were various rays of different refraction". At the same time, he believed that the subjective nature of color is as he said in his book "Optics": "Properly speaking, light is colorless, and there is nothing in it except a certain power and the nature of arousing a certain color sensation". Newton also studied the nature of surface color, saying: "The color of an object is nothing but the nature of reflecting a certain light more than the rest".

Newton also discovered two important facts, namely that the properties of light or wavelength are not changed by reflection or refraction, and that several separated wavelengths can be recombined to form "the same white light as before". He also demonstrated that the colors produced by the mixture of individual wavelengths show the same visual effect as a wavelength between these individual wavelengths, but he emphasized that the composition of the spectrum is different.

Newton tried to find a geometric method to derive the color of a mixture assuming that the number and quality of the primary colors are known. In this experiment, he arranged the colors on a disk and imagined that the center was a white point. However, perhaps because of the poor quality of his optical components, his experimental mixtures of two primary colors never produced white.

In these experiments, Newton laid the modern scientific foundation of colorimetry. Although Newton's experiments in using two or three primary colors to mix to form white failed, the law of three-color mixing was determined by Maxwell in 1860 in his research on the various wavelength spectra of different amounts of red, blue and green light. The primary colors are now called matching stimuli or reference stimuli.

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