In ancient times, humanity thought that we can see thanks to the tentacle rays that come out of our eyes, as if trying to touch objects. It seems ridiculous and funny. But really, what is light? Where does it come from? Distinguish between natural and artificial light sources. 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. During the propagation of light, its wave qualities are detected. We will talk about below.
Shine
What is it? Frankly, this is an electromagnetic wave. It is perceived by the eyes of man. True, there are boundaries of perception - from 380 to 780 nm. At lower rates, there is a flux of ultraviolet radiation, which a person cannot see, but senses. On the skin, it appears as a tan. There is also infrared radiation, which only some living organisms can see, and people perceive it as heat.
Light comes in different colors. If you recall the rainbow, she is the owner of seven colors. The violet color present in it is formed by a wavelength beam of 380 nm, red - 625, but green - 500, more than violet, but less than red. Many artificial light sources emit white-colored waves. White light occurs when all other primary colors are mixed - it is red, orange, yellow, green, cyan, blue and violet.
The 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. Due to this, sunlight through the atmosphere easily penetrates the earth. But at the same time he refracts. When an opaque body or object is encountered in the path of light, 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 precisely through sight. Thanks to him, we analyze everything. Good vision and a high level of performance are very much related to lighting.
Sources
The bodies from which light emanates are light sources. There are natural and artificial light sources. The most popular and vital natural light source is the Sun, namely solar radiation - the radiant flux of a star that reaches the surface of our planet in the form of direct and diffused light. In natural light, and more precisely in its spectrum, there are ultraviolet rays, which are simply necessary for humans. Diffusion is a characteristic feature of natural light. It is good for vision. After we figured out 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 began actively. For almost 130 years of their existence, the fire was almost completely supplanted - kerosene lamps and candles appeared. They are now used when there is an accident at the station, when the lighting suddenly disappears, for a romantic evening, to create an appropriate atmosphere. In camping trips, when the flashlights are discharged, they use a kerosene lamp. For more extensive lighting, you can make a fire.
Is bonfire an artificial or natural light source? It should be sorted out. The flame of burning dry twigs, as well as the flame of a candle, gas burner, and so on are artificial sources. I would like to note one feature. Artificial light sources can be controlled by people.
Let us reason like this: in principle, the fire burns on its own, giving off also heat. Near it, you can bask, see friends sitting opposite and singing with a guitar in the dark. It’s like a bonfire - it’s a natural source of light. He gives his unreflected light, like the moon. But then the fire starts to go out, there is a need to throw firewood. The more firewood, the greater the flame. So it can be controlled. Moreover, initially the campfire was created by tourists themselves. And artificial sources are those created by man. Hence the conclusion suggests itself: a bonfire is still an artificial light source.
Artificial are also technical devices of the most diverse structure. These are incandescent lamps, searchlights, electric lamps and more. There are bodies that cannot radiate on their own, but emit reflected light, such as the moon.
Let us consider in more detail which light sources are natural.
Natural sources
All objects from which natural light streams should be attributed to natural sources. They are the natural sources of light. It does not matter what the emission of waves is, 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:
- Sunlight.
- Fire, a natural source of light.
- Starlight.
- The glow of a variety of animal and plant organisms.
And this is not the whole list. You can also list natural light sources. Examples: The sun, scorching on a July day, the stars that can be observed at night and put them into bizarre constellations, lightning breaking open clouds, a comet with a magnificent tail or aurora, iridescent and amazing. Natural light can be considered glistening in the grass, like small grains of gold, insects and some species of fish, importantly swimming almost on the seabed.
Interstellar gas
A rarefied gas medium fills the space between the stars. Gas is transparent. The bulk of interstellar gas is observed closer to the plane of the galaxy. This layer has a thickness of many hundreds of parsecs. The chemical composition is similar to most stars - it is hydrogen, helium and a few heavy particles. Gas is in atomic, molecular and ionized form, it all depends on density and temperature. Gas absorbs ultraviolet rays, and in return they give it the available energy. Ultraviolet radiation from hot stars begins to heat the gas. Then the gas itself begins to emit light. A man observes it as a bright 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" is 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 photophores of fish, in special organoids in unicellular eukaryotes, in the cytoplasm in bacteria. Recall fireflies and some aquatic organisms that live on the bottom of the oceans (deep-sea cuttlefish, radiolaria). Bioluminescence is a product of chemical processes, energy that is released, while it begins to be released in the form of light. In other words, this 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 for the appearance of a radioluminescent layer in some substances. For example, dyes, which consist of a mixture of zinc sulfide and a source material 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, devices.
Light spread
Light does not have the ability to go around obstacles that it encounters in its path. It spreads in a straightforward manner. And no other way. Therefore, behind an object that does not have transparent properties, a shadow forms. The shadow is not always black. Since scattered and reflected rays of light that come from other objects fall there. This is especially well known to artists.
The rays of light are not able to pass through a dark barrier. For example, if the Moon is between the Sun and the Earth, hence solar eclipses arise.
Sources of light. Hot and Cold
Consider natural light sources. Examples of warm springs are the sun. It is not only the main source of light, but also heat. Therefore, in the understanding of mankind, light means heat. The red-hot lava, which quickly tends down the slope of the volcano, also emits a huge amount of heat, but there is slightly less light.
Everyone has met “cold” light in their life. This is aurora, fireflies, rotten. But the bodies of the owners of such light do not heat up.
Point light source
In the study of light phenomena, the concept of a “point source of light” appeared. It is not a discovery that all light sources have their size. A natural source of light is a 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 also like to note the natural sources of light in our mortal existence - it is joy and happiness! May they never leave you and illuminate your life path.