Chromatic, achromatic colors and their perception
All shades that are around us and which we distinguish can be divided into chromatic and achromatic colors. The achromatic are special, those that can not be obtained by mixing the main. To find out what achromatic colors are, let us first analyze which of them are called chromatic and main colors and why.
The word "chromatic" in Greek means "colored." It is possible to make a logical conclusion that chromatic include bright colors — red, orange, yellow, green, blue, blue, purple, and all their shades. Chromatic and form a color spectrum. All shades of this spectrum can be obtained by mixing the three main - red, yellow and blue - in various proportions. From these primary (primary) secondary and tertiary are formed. So all of the three colors obtained many other colors and shades.
Of the primary colors and their combinations is the color spectrum. It is customary to allocate 12 segments. The first segment - shades of red, the second - shades of orange, the third - shades of yellow-orange, and so on in a circle to purple and its variations. In such a spectrum, primary colors (they are primary) —you red, yellow, blue — secondary — orange, violet, and green — and tertiary, which are formed by mixing primary and secondary, are distinguished. So the usual bright rainbow spectrum is built.
Achromatic - "colorless"
The word "achromatic" in Greek means "colorless." Such a strange name at first glance received colors that are not formed by any combinations of primary or secondary. So what achromatic colors exist in nature? It is white, black and all possible shades of gray.
Due to the fact that they cannot be obtained with the help of the main ones, they were given such a paradoxical name - achromatic, although in reality the colorless of them is only white.
Although it is difficult to get white or black from the chromatic spectrum, it is possible to perform the reverse experience. If you take a prism and send a beam of white light to it, as a result of non-uniform refraction of the rays inside the prism, the chromatic spectrum is formed.This is a well-known beautiful optical experience, produced by Isaac Newton in the 17th century.
Our brain recognizes the bright colors of the spectrum, depending on the wavelength of light that reaches the visual center of the eye after reflection from a particular object. The fact is that an object of a certain color absorbs all tones except its own. For example, a yellow cup absorbs everything, but not yellow. It reflects it, and this reflected wave reaches our eyes and is perceived by the brain. Each chromatic color has a specific wavelength. Violet has the shortest electromagnetic wavelength - 360-390 nm, red - 680-720 nm. This range of lengths also forms visible light. What is beyond its borders is ultraviolet and infrared radiation, which the human eye does not perceive.
But how are achromatic colors perceived? The black color absorbs all other shades, that is, the reverse light flux from black bodies is absent, white reflects everything, here the light flux is the most intense. That is, achromatic - black and white - we perceive as the presence of an intense or complete absence of a reverse light flux.
It is precisely because of its ability to absorb the spectrum that black has long been associated with something mysterious, in various cultures it personifies death, depression, fear, and white, as opposed to it, is a symbol of clarity, purity, joy, motivation to act.