Why can we see colors?

The world is so wonderful in large part because we can see a wide variety of colors.

So have you ever thought about the question: is the same color the same in the eyes of different people? I believe many people have had this question because many times what we think looks good, others do not think it looks good, and what we feel is ugly, but some people can not turn their eyes to it. To get the answer to this question, we must first know why people can see color. We know that visible light has seven different colors, namely red, orange, red, green, blue, indigo and violet, and the first person to separate visible light was Isaac Newton.

Ordinary daylight looks white, and Newton used a prism to divide the white light into seven different colors, which is the dispersion experiment.

The reason why white light can be divided into different colors by the prism is that each color of light has a different wavelength, and the refractive index of light of different wavelengths is different. Now we know that white light is a combination of seven colors of light, but in the daily color mixing we do not need to use seven colors of light, but only three can, that is, we are familiar with the three primary colors of red, green and blue, the use of these three colors can be mixed with all the other colors, and the three colors of light overlap is also white.

Why use three colors of light that can be deployed in all the other colors?

The problem does not lie in the color itself, but in the process of perceiving color. People can see because they have eyes, and there are two types of cells in the human eye, one is called "optic rod cells" and the other is called "optic cone cells", the optic rod cells are responsible for perceiving light and the optic cone cells are responsible for perceiving color. The cone cells in the human eye can be divided into three types, one of which is most sensitive to light with a wavelength of about 560 nanometers, another is most sensitive to light with a wavelength of about 530 nanometers, and the third is most sensitive to light with a wavelength of about 440 nanometers.

Let go of the wavelength of light comparison table we will find that the wavelength 560 nm is red light, wavelength 530 nm is a green light, and wavelength 440 nm is blue light.

When red light enters our eyes, the red cone cells are stimulated and send signals to the brain, which processes the signals, and then we perceive the color red. If red and green light enters our eyes at the same time, the red and green cone cells are stimulated at the same time, and both send signals to the brain, at which time the brain receives both signals, so it makes up a feedback signal, and then we perceive the yellow color.

It is worth noting that the feedback signal of yellow is made up of the brain through the comprehensive processing of information, so it is a subjective feeling.

Since color is a subjective perception of the brain, it is reasonable to believe that different people may see colors differently, which is why some people like yellow while others express disgust with the color. Another support for the idea that "color is a subjective perception" is color blindness. Isn't it strange that when a person has a problem with their red cone cells, they have no way to distinguish between red and green, so they become red-green blind, but they can still see yellow?

The red cone cell has a problem, but can still see the yellow color made of red and green, this does not make logical sense.

But if color is a purely subjective perception, is the brain according to the signals received by their own "brain" out, then it makes perfect sense. Color is not only the brain's subjective perception, the brain will adjust this feeling according to external information, for example, if a color represents positive things in the long term, we will gradually like this color