In ancient times, mankind thought that we can see thanks to the rays-tentacles that come out of the eyes, as if trying to touch objects. It seems ridiculous and funny. But really, what is light? Where does it come from? There are natural light sources and artificial ones. Modern ideas say that light is electromagnetic waves or a stream of photons. In fact, light is radiation, but that part of it that can be perceived by the eye. That is why it is called visible radiation. When light propagates, its wave qualities are revealed. Which we will talk about below.
Light
What is this? To put it bluntly, this is an electromagnetic wave. It is perceived through the eyes of a person. True, there are limits of perception - from 380 to 780 nm. At lower rates, there is a stream of ultraviolet radiation that a person cannot see, but feels. On the skin, it appears as a tan. There is also infrared radiation, which only some living organisms can see, and by humans itperceived as warm.
Light comes in different colors. If you remember the rainbow, it is the owner of seven colors. The violet color present in it is formed by a beam of wavelength 380 nm, red - 625, but green - 500, more than violet, but less than red. Many artificial light sources emit white waves. White light occurs when all other primary colors are mixed - red, orange, yellow, green, cyan, indigo and violet.
Properties
Thanks to experiments, it was possible to establish that light has an electromagnetic nature. Simply put, light is electromagnetic radiation that can be seen.
Light boasts that it has the ability to pass through transparent substances and bodies. This makes it easy for sunlight to reach the earth through the atmosphere. But at the same time, it breaks down. When an opaque body or object is encountered in the path of light, the light is reflected from them. Thus, we take the reflected color with the eye and see not only the color, but also the shape.
A certain part of the light is absorbed by objects, and they heat up. Light objects do not heat up as much as dark ones, as they absorb more light and reflect less. That is why they look dark. The lion's share of the information that surrounds us comes through vision. Thanks to him, we analyze everything. Good vision and a high level of performance are very much related to lighting.
Sources
Bodies from which emanateslight, and are sources of light. There are natural and artificial light sources. The most popular and vital natural source of light is the Sun, namely solar radiation - the radiant stream of a star that reaches the surface of our planet in the form of direct and diffused light. In natural light, or to be more precise in its spectrum, there are ultraviolet rays that are simply necessary for humans. Diffuseness is a characteristic feature of natural lighting. This is good for the eyes. After we have de alt with many concepts, we can begin to explain what it is - artificial and natural light sources.
Artificial sources
Until the end of the 19th century, the only artificial source of light was fire, in all its interpretations. Later, the rapid development of electric light sources actively started. For almost 130 years of their existence, fire was almost completely replaced - kerosene lamps and candles appeared. They are still used when there is an accident at the station, when the lighting suddenly goes out, for a romantic evening, to create the appropriate atmosphere. In hikes, when the lanterns are discharged, they use a kerosene lamp. For more extensive lighting, you can build a fire.
Campfire - artificial or natural source of light? Should be sorted out. The flame of burning dry branches, as well as the flame of a candle, a gas burner, and so on, are artificial sources. I would like to point out one feature. Artificial light sources can be controlled by people.
Let's think like this: in principle, a fire burns on its own, giving off heat as well. You can warm yourself near it, see friends sitting opposite and singing to the guitar in the dark. A fire is a natural source of light. He gives his unreflected light like the moon. But then the fire starts to go out, it becomes necessary to throw firewood. The more wood, the bigger the flame. So they can be controlled. Moreover, initially the fire was created by the tourists themselves. And artificial sources are those created by man. This leads to the conclusion: a fire is, after all, an artificial source of light.
Technical devices of the most diverse structure are also artificial. These are incandescent lamps, spotlights, electric lamps and so on. There are bodies that cannot radiate on their own, but emit reflected light, such as the Moon.
Let's take a closer look at which light sources are natural.
Natural sources
All objects from which natural light flows should be attributed to natural sources. They are natural sources of light. It doesn't matter what kind of wave emission is going on, as a primary or secondary property. Natural light sources play a huge role in the life of all living organisms. Natural sources in nature are not controlled by man:
- Sunshine.
- Fire, natural source of light.
- Starlight.
- The glow of a variety of animal and plant organisms.
And this is far fromthe whole list. You can list more natural sources of light. Examples: The sun scorching on a July afternoon, stars that can be seen at night and stacked in bizarre constellations, lightning tearing loose clouds, a comet with a magnificent tail or aurora, iridescent and admirable. Natural light can be seen glimmering in the grass like small grains of gold, insects, and some species of fish importantly swimming almost on the sea floor.
Interstellar gas
The rarefied gaseous medium fills the space between the stars. The gas is transparent. The main part of the interstellar gas is observed closer to the plane of the Galaxy. This layer is many hundreds of parsecs thick. The chemical composition is similar to most stars - it is hydrogen, helium and some heavy particles. The gas is in atomic, molecular and ionized form, everything depends on density and temperature. The gas absorbs ultraviolet rays, and in return they give it the available energy. Ultraviolet radiation from hot stars begins to heat the gas. The gas itself then begins to emit light. Man observes it as a light nebula.
Bioluminescence
The tricky word denotes the ability of living organisms to glow. This skill is achieved independently or with the help of symbionts. The Greek word "bios" means life. And the Latin "lumen" - light. Such a talent as the creation of light does not belong to everyone. This requires specially luminous organs and the possession of a more developed organism. For example, in fish photophores,in special organelles in unicellular eukaryotes, in the cytoplasm in bacteria. Let's think about fireflies and some aquatic organisms that live at the bottom of the oceans (deep-sea cuttlefish, radiolaria). Bioluminescence is a product of chemical processes, the energy that is released begins to be released in the form of light. In other words, it is a special kind of chemiluminescence.
Radioluminescence
This process is caused by the influence of ionizing radiation. Such chemical compounds that emit gamma and X-rays, alpha, beta particles, are used to create a radioluminescent layer in some substances. For example, dyes, which consist of a mixture of zinc sulfide and a source of ionizing radiation, emit light for a long period of time. This period is measured in years and even decades. Such substances are widely used in special paints. They covered the dials of watches and instruments.
Spreading light
Light does not have the ability to bend around obstacles that it encounters on its way. It spreads in a straight line. And nothing else. Therefore, a shadow is formed behind an object that does not have transparent properties. The shadow is not always black. Since scattered and reflected rays of light that come from other objects get there. Artists know this especially well.
Rays of light cannot pass through a dark barrier. For example, if the moon is betweenSun and Earth, hence solar eclipses.
Sources of light. "Hot" and "cold"
Consider natural light sources. An example of warm sources is the Sun. It is not only the main source of light, but also heat. Therefore, in the understanding of mankind, light means heat. Hot lava, which quickly rushes down the slope of the volcano, also releases a huge amount of heat, but slightly less light.
"Cold" light in his life everyone met. This is the aurora, fireflies, rotten. But the bodies of the holders of such light do not heat up.
Point light source
When studying light phenomena, the concept of "point source of light" appeared. It is not a discovery that all light sources have their own size. The natural source of light is the star. The sun is a yellow dwarf. There are stars much larger, but they are perceived by people as point sources of light, because they are at a huge distance from our planet.
In conclusion, I would like to note the natural sources of light in our mortal existence - this is joy and happiness! May they never leave you and illuminate your life path.
