"And God said," Let there be light! "And the light became." Everyone knows these words from the Bible and everyone understands: life without it is impossible. But what is light in nature? What does it consist of and what properties does it have? What is visible and invisible light? We will discuss these and some other issues in the article.
On the role of light
Most information is usually perceived by a person through the eyes. All the variety of colors and shapes that are characteristic of the material world is revealed to him. And he can perceive through vision only that which reflects a certain, so-called visible light. Light sources can be natural, such as the sun, or artificial, created by electricity. Thanks to such lighting, it became possible to work, relax - in short, to lead a full-fledged lifestyle at any time of the day.
Naturally, such an important aspect of life occupied the minds of many people who lived in different eras. Consider what light is, from different angles of view, that is, from the standpoint of various theories that scientists today adhere to.
Light: definition (physics)
Aristotle, who asked this question, considered light to be a specific action that spread in the medium. Another opinion was held by a philosopher from Ancient Rome, Lucretius Car. He was sure that everything that exists in the world consists of the smallest particles - atoms. And light also has such a structure.
In the seventeenth century, these views formed the basis of two theories:
Newton adhered to the corpuscular theory . His formulation of what light is is as follows. Luminous bodies emit tiny particles distributed along lines, that is, rays. They get into the eyes, thanks to which people see.
Another theory is associated with the name Huygens. He believed that there is a special environment where the law of gravity does not apply. In it between the particles there is a luminiferous ether. That's what light is, in his opinion.
Despite a different explanation, today both theories are considered correct and are studying them. Light has both wave and partial properties.
Visible light frequency
Light is the spectrum of electromagnetic waves available to the eye. If you look at the scale of electromagnetic radiation, it turns out that visible light occupies a very insignificant place on it. It turns out that only a small part of what is radiated is accessible to man. It is important to note here that the specified range is available specifically for the person. That is, perhaps some animals, for example, can see inaccessible to people. And vice versa. Human vision is able to see colors that individual animals cannot see.
Infrared rays
The English scientist Herschel in 1800 laid out sunlight in the spectrum. A mercury tank on one side was blackened with soot. Observations showed an increase in temperature. Because of this, he decided that the thermometer was heated by rays invisible to the human eye. Subsequently, they were called infrared, that is, thermal.
This effect perfectly illustrates the spiral furnace. When heated, it begins to warm first, without changing color, and only then, when glowing, blush. It turns out that the range of the spiral varies from infrared invisible to ultraviolet radiation.
Today it is known that all bodies emit infrared light. Light sources emitting infrared rays have a longer wavelength, but a weaker angle of refraction than red ones.
Heat is infrared radiation emanating from moving molecules. The higher their speed, the greater the radiation, and such an object becomes warmer.
Ultraviolet
As soon as infrared radiation was discovered, Wilhelm Ritter, a German physicist, began to study the opposite side of the spectrum. The wavelength here turned out to be less than that of the violet color. He noticed how silver chloride turned black behind violet. And this happened faster than the wavelength of visible light. It turned out that such radiation occurs when the electrons on the outer atomic shells change. Glass is capable of absorbing ultraviolet light; therefore, quartz lenses were used in studies.
The radiation is absorbed by the skin of a person and an animal, as well as by the upper plant tissues. Small doses of ultraviolet light can have a positive effect on well-being, strengthening immunity and creating vitamin D. But large doses can cause skin burns and damage to the eyes, and too large even have a carcinogenic effect.
UV application
Ultraviolet radiation is used in medicine (it can kill harmful world organisms), for tanning, as well as in photographs. When absorbed, the rays become visible. Therefore, another of its scope is the use in the manufacture of fluorescent lamps .
Conclusion
Given the negligible spectrum of visible light, it becomes clear that the optical range of a person has been studied very poorly. One of the reasons for this approach is people's increased interest in what is visible to the eye.
But because of this, understanding remains low. The whole cosmos is penetrated by electromagnetic radiation. More often people not only do not see them, but also do not feel them. But if the energy of these spectra increases, then they can cause malaise and even become deadly.
When studying the invisible spectrum, some, as they are called, mystical phenomena become clear. For example, ball lightning. It happens that they, as if from nowhere, appear and suddenly disappear. In fact, the transition from the invisible range to the visible and vice versa is simply carried out.
If you use different cameras when taking pictures of the sky during a thunderstorm, you can sometimes capture the transition of plasmoids, their appearance in lightning and the changes that occur in the lightning itself.
Around us is a completely unexplored world that looks different from what we are used to seeing. The well-known statement “Until I see it with my own eyes, I will not believe it” has long lost its relevance. Radio, television, cellular communications and the like have long proved that if we don’t see something, this does not mean at all that this does not exist.