The original Display Monitor comes from The birth of Color and Light

Why can our eyes see?

The essential answer is survival.

Actually Light is an electromagnetic wave. The eye is the instrument by which we accept this electromagnetic wave.

At present, human beings have observed and thought that everything in the universe affects each other through four extremely mysterious forces. One of them is named electromagnetic force. Electricity, magnetism, light, etc. are all electromagnetic forces. (The other three mysterious forces are strong interaction, weak interaction, and gravity).

Because to tell the truth, how and why these four mysterious forces came about in the first place is unknown to mankind. So we just need to know that everything in the universe is harming each other in a way called electromagnetism. And this ability to exert influence is energy.

However, how does this mysterious energy spread? Intelligent human beings have observed and thought about it and found that "as if" is like water waves that spread in all directions, so it is vividly called an electromagnetic wave. And we found that the transmission of this mysterious force has a minimum unit, so we named this minimum unit the photon, like hazelnut or a melon seed. Imagine a million little melon seeds spreading out like waves in all directions.

Okay, but still don't understand why we can see.

Allow me to finish. This mysterious electromagnetic force has large and small waves, the size of which is the wavelength of the cup. Like water waves, large waves vibrate slowly, small waves vibrate fast, and faster waves exert greater influence and energy. For us humans, bigger waves are not always better, and certainly not always smaller.

Some waves of size are "good waves" that will bring us good effects, while others of size are "bad waves" that will bring us harm. Some bad waves are so powerful that they can kill us in minutes.

People who like to give names to the "good waves" that the eye can receive have another name: light.

The eye catches these light waves, catching the cute little photons. The photon contains mysterious cosmic energy that, when it reaches our eyes, stimulates our nerves and produces a signal that reaches our brains, telling us: there are good waves!

But the "good waves" coming from the sun and penetrating the atmosphere is not just one size, but a combination of many different sizes, arranged according to the wavelength, like the one below, which ranges from 390 to 700 nanometers, which our eyes can pick up.

If you put this above into a broader spectrum of electromagnetic waves, it looks something like this. Wow, visible light is only a small part of electromagnetic waves!

The image above is called a spectrogram, and the color portion in the middle is the arrangement of visible light by wavelength from small to large (left to right). You'll notice that we've painted different waves in different colors. Why is that?

We rely on the eye, we find the good bobo, and then what? Where is the food?

Depending on the nature of the object, some wavelengths of light may be absorbed, some may pass through, and some may be reflected (more on that later), resulting in different amounts of light coming from different objects and entering our eyes. What does that mean? This means that as long as we humans can analyze these different wavelengths of light and build a database based on our experience, we can identify our surroundings from them, and the speed of light is very fast, which means that our knowledge of the surroundings is very timely. Not only can we find food faster and more accurately, but we can also avoid danger! This ability is great!

How do you get this ability? Evolution is very easy. Said earlier, the size of different wave energy is also different, our brains evolved the ability to analyze the size of these energies, these waves into our eyes, different energy will produce different signal, through the analysis of the signal, we can determine what this is is a wave: Northrop, this wave is wavelet, this wave is medium wave, the wave is big Bob. But it was hard to distinguish and communicate, so our ancestors gave these waves nice names: purple, blue, green, yellow, orange, red, and so on. That's the idea of color.

And then we can establish a database, based on experience of the "green" "red" above the "tree" of the fruit is edible, is the translation of a wavelength at about 550 nm light above the "tree" of the object appeared some at around 700 nm wavelength light circular object, according to the data analysis, intake of these circular object is to provide energy, can give the body to eat.

What is the color? Remember, humans, are foodies! Color, to put it bluntly, is the concept we create to distinguish the wavelengths of light emitted by different objects in order to eat!

Light passes through the cornea and lens and reaches the retina, producing signals that tell the brain that Light is "coming.

There are four types of cells in the retina that sense light, called L/M/Scones and Rod cells.

L/M/S main senses the difference in the wavelength of the light during the day, While Rod senses the brightness of the light at night. (this combination is basically equivalent to the double camera of mobile phone, we will talk about the details later) Their sensitivity to marketers' wavelengths of light is too.

(some people don't take these cells called L/M/S, but called R/G reen)/B (Ed) (blue) cells, used to say they can feel the color of the light, but this is not serious, and each cell is the most sensitive wavelength peak is not red, green and blue, but the yellow, green, purple, because each color is a result of the combined action of three kinds of cells, not single attribution to one of the cell. So we use the expression L/M/S.

The number of cones is relatively small, with L/M cells very concentrated in the center of the retina, and S cells relatively few but more sensitive. Cones are mainly responsible for determining the wavelength and precise location of light during the day, but not at night.

Rod cells are very numerous, distributed around the retina, because of special sensitivity, so only when the light is dark can work well, when the light is too bright will be bright blind. Mainly responsible for the amount of light at night which is light and dark.

A long, long time ago, humans discovered that they could not live without sunlight, so we evolved the eye, and in the eye, we had a cone cell called L.

What's the use of this L cell? The cell senses the presence of light and is most sensitive to the highest concentrations of sunlight at wavelengths around 560 nanometers.

With this tool, awesome, as long as the human head, you know, hey ~, this side of the sun, go that way! We can also "see" objects, as long as the light coming from them is within the range of what the L cell senses.

At this point, we find that the eye gives us three different senses, no sense of light at all, a sense of being stimulated evenly by various wavelengths, and a sense of being somewhere in between.

We call the first sensation black, the second white, and the third gray.

Why do we humans find black scary? Just because the idea of black comes from the absence of light, no light, no energy, no energy, we're screwed,

But because we only have one L cell, we can't really tell the wavelength of light apart, in other words, it's not enough information, so a lot of things look the same, like this.

This is not good, ah, a lot of food is also indistinguishable. And to the length of the light is very insensitive, the sea, the blue sky, can not see, black, accidentally fell in the ditch, eat the wrong thing to eat diarrhea to pull to death, in short, the survival rate is not high.

At this point, some humans mutated and another type of cell, the S cell, appeared in the eye.This cell can sense light at shorter wavelengths, and is most sensitive to light at wavelengths around 420nm.

This is even more remarkable, because with two inputs, the short-wavelength light is clearly felt, and our brains are able to distinguish between the longer wavelengths and the shorter wavelengths, and the world feels something like this.

At this time, we humans, on the basis of black, white and gray, have developed a more advanced sense of "color", which can be used to distinguish the length of the wavelength of light. We call the feeling of sky and sea blue, and the feeling of apple and trees yellow.

Specifically, light with a wavelength shorter than 492nm mainly stimulates S cells. This sensation is what we call blue and light with a wavelength longer than 492nm mainly stimulates L cells. This sensation is what we call yellow!

The sun's rays evenly stimulate both of our cells. This sensation is still called white, and the sensation without light is still called black. What had been gray turned into varying shades of blue and yellow.

But what if the wavelength of light is about 492nm?This is the point where the sensitivity of the L and S cells overlap, so both types of cells are stimulated at the same time, and this wavelength of light is going to give us the sensation of sunlight, and we're going to feel white.

Humans with this S cell are significantly better at understanding their surroundings, finding food, and avoiding danger in a more timely manner than humans with only L cells. So this species survived better, and humans evolved.

So many fruits look the same, ripe apples are indistinguishable from unripe ones, and plums and grapes are indistinguishable from each other. How to do?

Evolution!

So our L cells began to mutate, and a very similar cell, M, appeared, but with a slightly shorter wavelength, concentrated at about 530 nanometers.

So we have three kinds of cells in our retinas, and for the same wavelength of light, our brain gets three kinds of signals, and this third kind of signal gives us more sensation, and further experience the difference in light based on the original dichotomy.

First of all, our original short wave and long wave are different from the past, in the past, whenever the L signal is strong, the long wave is yellow, and whenever the S signal is strong, the short wave is blue.

Now on the long-wave side, we have two signals, one L and one M, and our brain will combine the values of these two signals and compare them with the values of the S signal to see if it's a long wave or a short wave, which is about 500 nanometers in the middle.

Before you feel (that is, in the long wave of yellow), on the basis of the above 500 nm wavelength range, L and M cells signal will have different, above the 590 - nm wavelength, L cell signal is stronger than the feeling of M cells is a kind of new feeling, this feeling we named red, between 570 nm and 500 nm wavelength, L cell signal is weak in the sense of M cells signal, we named the green.When there is no difference between the L signal and the M signal (about 570~590nm), it feels the same as before.

In addition, the feeling of the transition from yellow to pure red from 590 to 620 is called Orange, which helps distinguish oranges from apples.

In the scope of the original feeling blue, that is, under 500 nm wavelength range, from 390 nm to 450 this range, the signal is stronger than L M signal (see image below again), the feeling and blue (SW) together, forming a new feeling, we named the Purple (Violet, attention is not Purple, of course, this part is likely to contain our Chinese blue) if the wavelength is 500 nm, the feeling of long wave and short wave, are neither yellow or blue, at this point, is pure M signal is stronger than L signal feeling, We call this feeling Cyan., within the range of 450 ~ 500 nm this feeling in transition from purple to blue, with around 477 nm, L and M signal intensity, person's feeling is affected by the S signal, only this time the feeling is pure blue, we Chinese people usually call before and after the wavelength of many colors are blue, divided into dark blue and light blue.

As for the reason why L and M are a little more receptive in the short-wave range, it is because the wavelength of light at this band is short and high in energy, and some of it may be absorbed by retinal cells, which then release weaker photons with longer wavelengths, which then stimulate L and M cells.

Again, sunlight stimulates all three types of cells at the same time, L/M/S, which we define as white. None of the three sensations are stimulated, which we define as black.

All of this, if you have to look at a graph, looks like this. The yellow ones are longer than the shorter ones, the blue ones are the other way around, the red ones are the L's stronger than the M's, and the green ones are the other way around.

With the ability to distinguish the above, we humans the biggest gain is: can distinguish the green apple and the red apple.

Before there were M cells, we saw red apples and green apples as follows, no difference, often eat sour apples, with M cells, wow, the whole world is different! Mom doesn't worry about my teeth anymore.

So the human survival rate was significantly improved, good Happy!

Oh, almost forgot, not to discover, not light during the day activities, also have a nightlife, hide a lot of wild animals, but in the evening the dark was eaten don't watch carefully, terrible! Have to do? You know the answer: evolution!

Because the night is particularly dangerous, so must be very sensitive, with a little bit of light to see clearly around the moon.

So gradually, the human retina grew a lot of these rod cells, and these cells are very sensitive, and they can capture a photon, much more sophisticated than a precision instrument. When the L/M/S cells don't feel anything, the rods provide us with signals, but because they're alone, as they were in the early days of humans, they can't distinguish between wavelengths. But at this point it doesn't matter whether the color is red or not, it doesn't matter whether the apple is red or not.

Because the rods are derived from S cells, they are naturally more sensitive to short waves, which is why we tend to see blue when the light is low.

Thanks for reading, the next article will show Monitor how to control color and light.