"And God said, 'Let there be light!' and there was light." Everyone knows these words from the Bible and everyone understands: life without it is impossible. But what is light in its nature? What does it consist of and what properties does it have? What is visible and invisible light? We will talk about 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 forms 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 a word, 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, that is, from the standpoint of various theories that pundits adhere to today.
Light: definition (physics)
Aristotle, who asked this question, considered light to be a certain action, whichspread in the environment. A different opinion was held by the philosopher from Ancient Rome, Lucretius Carus. He was sure that everything that exists in the world consists of the smallest particles - atoms. And light also has this structure.
In the seventeenth century, these views formed the basis of two theories:
- corpuscular;
- wave.
Corpuscular theory adhered to Newton. His formulation of what light is is as follows. Luminous bodies radiate the smallest particles distributed along lines, that is, rays. They get in the eyes, so people see.
Another theory is associated with the name of 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, according to him.
Despite the different explanations, today both theories are considered correct and are being studied. Light has both wave and particle properties.
Visible light frequency
Light is the spectrum of electromagnetic waves available for perception by the eyes. If you look at the scale of electromagnetic radiation, it turns out that visible light occupies a very small place on it. It turns out that only a small part of what is radiated is available to a person. It is important to note here that the indicated range is available specifically for humans. That is, perhaps some animals, for example, can see inaccessible to people. And vice versa. Human vision can see colors that individual animals cannot see.
Infrared rays
The English scientist Herschel in 1800 decomposed sunlight into a spectrum. The mercury tank was blackened on one side 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 furnace spiral. When heated, it first begins to warm up, without changing color, and only then, when heated, blush. It turns out that the range of the spiral varies from invisible infrared 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 from moving molecules. The higher their speed, the more 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 shorter than that of the violet color. He noticed how the silver chloride turned black behind the violet. And it 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, so quartz lenses were used in the research.
Radiation is absorbed by human skin andanimal, as well as upper plant tissues. Small doses of ultraviolet radiation can have a beneficial effect on well-being, strengthening the immune system and creating vitamin D. But large doses can cause skin burns and damage the eyes, and too much can even have a carcinogenic effect.
Ultraviolet applications
UV radiation is used in medicine (it is able to kill harmful micro-organisms), for tanning, and also in photographs. When absorbed, the rays become visible. Therefore, another area of its application is the use in the production of fluorescent lamps.
Conclusion
If we take into account the negligibly small spectrum of visible light, it becomes clear that the optical range has been studied very poorly by man. 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 at a low level. The entire cosmos is permeated with 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 illness and even become deadly.
When studying the invisible spectrum, some, as they are called, mystical phenomena become clear. For example, fireballs. It happens that they, as if from nowhere, appear and suddenly disappear. In fact, the transition from the invisible range to the visible range and vice versa is simply carried out.
If you use different cameras when taking pictures of the sky during a thunderstorm, sometimes it turns outcapture the transition of plasmoids, their appearance in lightning and the changes that occur in lightning themselves.
Around us is a world completely unknown to us, which looks different from what we are used to seeing. The well-known statement “Until I see it with my own eyes, I won’t believe it” has long lost its relevance. Radio, television, cell phones and the like have long proven that just because we can't see something doesn't mean it doesn't exist.
