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The material world is brilliant, and we can see all kinds of substances when we open our eyes.

In the park, we can look at the blue sky and white clouds, enjoy the waves of the lake, or observe the weeds and strange rocks, and meet a few relatives and friends. All of this is made of matter, which we have long known, but how do we distinguish between matter and matter?

The most important way of discrimination, of course, is to see-different substances can emit or reflect unused light, and it is by reacting to this light that our eyes finally recognize what they are, or recognize familiar people from a distance.

This mode of action is based on the interrelation of matter and energy, and most of the instruments we can use today make use of similar principles.

One of the most commonly used methods is called "spectral analysis," which we have previously described as seeing helium from the sun by analyzing and identifying characteristic spectral lines of its radiation.

Spectrum, as its name implies, is a spectrum arranged according to the wavelength of light. It is a pattern that records the emission or absorption of light waves by a certain substance. To identify substances according to spectrum is like singing songs by watching music. The forms of spectrum are very diverse, because there are too many ways for substances to change energy. Electronic transition is only the most common one. Our eyes usually play their role according to this point.

For example, when we go to enjoy flowers, colorful flowers stand on the branches surrounded by green leaves, and our eyes can really see each flower, which is a spectrum formed by visible light. In this process, the observation device is our eyes, and the recognition device is the processing system in the brain.

Source: pexels In these flowers and their leaves, there are many different pigment molecules. These molecules are made up of atoms, and the electrons in each atom undergo transitions when they absorb light. As mentioned earlier, the electron transitions must follow certain energy levels, which are quantized. So when sunlight hits, photons that don't have enough energy for electrons to jump between energy levels aren't absorbed and usually bounce back. Thus, the colors we see are the colors that remain after the pigment molecules have absorbed the desired light.

The eye itself is also a place where energy interacts with matter. In the case of the human eye, most visual systems have three light-sensitive structures called "receptors," which contain substances that interact with different colors of light and send signals to the brain, which recognizes red, green and blue. In fact, most electronic devices are designed in this way, such as computer screens, which can also emit three colors of red, green and blue. They can be blended into various visible light including white according to different proportions.

If humans could see only two colors, then we would be able to identify far fewer substances-and indeed many people are born colorblind, lacking certain photosensitive components, which has many disadvantages for life ("colorblindness" was first discovered by Dalton, so colorblindness is also called "Dalton disease," and Dalton's relatively low level of experimentation may have contributed to this).

Q: What numbers are on the map? On the contrary, if there are more photosensitive components, it will be easier to observe changes in the substance. Birds and some reptiles have four or more receptors in their eyes, and they see more of the world than we do. However, after mastering the laws of the interaction between energy and matter, humans made up for these shortcomings with detection instruments.

Many substances have electronic transitions outside the visible light range, that is, they absorb light that we cannot see, so that they appear to us as either plain white, gray, or black, or simply transparent.

Glass is a good example of how we occasionally bump into glass because it looks empty. However, this does not mean that there are no electronic transitions in the interior of the glass, just because they absorb very short light waves, ultraviolet light with higher frequencies than visible light, but have no interest in visible light, so we see glass as clear as water. If our human eyes could see ultraviolet light, we might see glass similar to bronze.

For these substances that cannot be distinguished by the naked eye, ultraviolet spectroscopy instruments can easily see the difference between them, which is an extension of our eyes.

Source: pexels In addition to ultraviolet spectroscopy, there are various spectrometers such as infrared spectroscopy, Raman spectroscopy and fluorescence spectroscopy, all of which can help us see substances clearly. All of them exploit the principle that electrons undergo transitions under the action of energy. Even in the visible light region, there are many substances that require instrumental help to see what they are-which is how we find helium in the solar spectrum.

Say light again. Essentially, what we mean by light is visible light, ranging from violet to red. Broadly speaking, light is not only visible light, but also infrared and ultraviolet rays. Although infrared rays, ultraviolet rays and electromagnetic waves outside their wavelengths cannot cause human vision, electromagnetic waves in ultraviolet and infrared bands can be effectively converted into visible light, and the existence of objects emitting such light can be measured or detected by optical instruments or photography and photography. Therefore, in the field of optical research, the concept of light is usually extended to electromagnetic radiation in the vicinity of visible light (infrared rays and ultraviolet rays), and even X-rays are considered light.

However, the influence of energy on the material world goes far beyond this. Our lives are constantly experiencing changes in energy.

Source: "Teaching Material Science to Teenagers"

Author: Sun Yafei

Some of the pictures in this article come from the Internet

copyright belongs to the original author

Editor: Zhang Runxin

This article comes from Weixin Official Accounts: Origin Reading (ID: tupyread), Author: Sun Yafei

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