What is light? Light, light sources. sunlight

"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 nature? What does it consist of and what properties does it have? What is visible and invisible light? We'll talk about these and some other issues in the article.

On the role of light

Most of the information is usually perceived by the person through the eyes. All the variety of colors and forms that are characteristic of the material world is revealed to him. And it can only perceive through sight what reflects a certain, so-called visible light. Sources of light can be natural, for example the sun, or artificial, created by electricity. Thanks to this lighting it became possible to work, rest - in short, to lead a full-fledged way of life at any time of the day.

Naturally, such an important life aspect occupied the minds of many people who lived in different epochs. Consider what light is, from different angles of view, that is, from the positions of the various theories that scientists today adhere to.

Light: definition (physics)

Aristotle, wondering about this question, considered light to be a certain action that spread in the environment. A different opinion was held by the 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:

• Corpuscular;
• wave.

Corpuscular theory was adhered to by Newton. His formulation of what light is, is the following. The glowing bodies emit the smallest particles, distributed along the lines, that is, the rays. They fall into the eyes, thanks to this people see.

Another theory is associated with the name Huygens. He believed that there is a special environment where the law of gravitation does not apply. There is a light-bearing aether between the particles. That's what light is, in his opinion.

Despite the different explanation, today both theories are considered correct and study them. Light has both wave and partial properties.

Frequency of visible light

Light is the spectrum of electromagnetic waves accessible to 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 accessible to a person. It is important to note here that this range is available for a person. That is, perhaps some animals, for example, can see that people can not. And vice versa. Human sight is able to see colors that individual animals can not see.

Infrared rays

English scientist Herschel in the year 1800 decomposed the sunlight into the spectrum. The 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 is perfectly illustrated by the furnace spiral. When heated, it begins to warm up at first, without changing the color, and only then, when incandescent, it turns red. It turns out that the range of the spiral varies from infrared to invisible to ultraviolet radiation.

Today it is known that all the bodies spread infrared light. Light sources, emitting infrared rays, have a longer wavelength, but the refraction angle is weaker than the red ones.

The heat is the radiation of the infrared spectrum emanating from the 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 was less than in violet. 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 external atomic shells have changed. Glass can absorb ultraviolet, so quartz lenses were used in the studies.

Radiation is absorbed by the skin of man and animal, as well as by upper plant tissues. Small doses of ultraviolet can have a beneficial effect on health, strengthening immunity and creating vitamin D. But large doses can cause skin burns and damage your eyes, and too much even have a carcinogenic effect.

Application of ultraviolet

Ultraviolet radiation is used in medicine (it is capable of killing harmful organisms), for sunbathing, and also in photographs. Upon absorption, the rays become visible. Therefore, another sphere of its application is the use of daylight in the production of lamps .

Conclusion

If we take into account the negligibly small 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 the increased interest of people in what is visible to the eye.

But because of this understanding remains at a low level. The whole space is permeated with electromagnetic radiation. More often than not people do not see them, but they do not feel it either. But if the energy of these spectra increases, they can cause malaise and even become deadly.

When studying the invisible spectrum, some, as they are called, mystical phenomena become understandable. For example, fireballs. It happens that they, as if from nowhere, appear and suddenly disappear. In fact, simply a transition is made from the invisible range to the visible and back.

If you use a different camera when taking photographs of the sky during a thunderstorm, sometimes it turns out to capture the transition of plasmoids, their appearance in lightning and changes occurring in the 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 with my own eyes, I will not believe" has long ago lost its relevance. Radio, television, cellular communication and the like have long proved that if we do not see something, it does not mean that it does not exist.