Light - extremely important kind of energy. The life on the Earth depends on energy of a sunlight. Besides, light is a radiation which gives us visual sensations.
We see subjects when light from them reaches our eyes. These subjects or radiate light, or reflect light radiated by other subjects, or pass it through itself. We see, for example, the Sun and stars because they radiate light. The majority of subjects round us we see thanks to light reflected by them. And some materials, such as stained-glass windows, open riches of the colours, passing light through itself.
the Bright sunlight seems to us purely white, that is colourless. But here we are mistaken, as this world consists of many colours. They happen, are visible, when sun beams, shine rain drops, and we observe a rainbow. The multi-coloured strip is formed and when the sunlight is reflected from oblique edge of a mirror or passes through a glass ornament or a vessel. This strip is called as a light spectrum. It begins with red colour and, gradually varying, comes to an end on the opposite end with the violet.
Usually we do not take into consideration weaker shades of colour and consequently we consider that the spectrum consists all of seven colour strips. The colours of a spectrum named seven colours of a rainbow, include red, orange, yellow, green, blue, dark blue, violet.
In the sixties ХVII centuries Isaak Newton made experiments with light. To spread out light to components and to receive a spectrum, it used a trihedral glass prism. The scientist has found out that, having collected the shattered beam by means of the second prism, it is possible to receive this world again. So it has proved that this world is a mix of different colours. Passing through a prism, light beams refract. But beams of different colour refract in different degree - red in the least, violet in the greatest. For this reason, passing through a prism, white colour is split up for compound colours.
Light Refraction is called as a refraction, and this world decomposition on different colours - a dispersion.
The Light spectrum - only a part of a huge range of radiations which is called as an electromagnetic spectrum. It includes scale, x-ray, ultra-violet, infra-red (thermal) radiation and radio-waves. All kinds of electromagnetic radiations extend in the form of waves of electric and magnetic fluctuations with a velocity of light - about 300 000 km/s. Electromagnetic waves differ among themselves mainly with length of a wave. It is defined by frequency, that is speed from which these waves are formed. The above frequency, the is more close to each other they settle down and the less length of each of them. In a spectrum light waves take a place between areas of infra-red and ultra-violet radiation.
The Image in cameras and optical tools receive, using lenses and the refraction phenomenon in them of light beams. Probably, you have noticed that in lenses of cheap telescopes, for example, round image contours the colour border is formed. There is it because, like a prism, the simple lens made of one piece of glass or plastic, refracts beams of different colour in different degree. In better devices this defect is eliminated by use of two lenses connected together. The first part of such compound lens decomposes this world to different colours, and the second again connects them, cleaning a border.
This world can be received, having mixed seven colours of a rainbow. But it can be made and is easier, having mixed only three colours - red, green and dark blue. They are called as primary colours of light. We will receive other colours, combining the cores. So, for example, the mix red with the green gives the yellow.
That fact that this world consists of several colours, explains, why we see subjects in this or that colour. For simplicity we will assume that this world consists only from red, green and dark blue. We see a subject white if it reflects all three making parts of this world, and black if it does not reflect any of them. But the red subject shined with this world, sees red because it reflects mainly a red component of white colour and absorbs the majority of dark blue and green components. In the same way the dark blue subject reflects dark blue beams, absorbing, red and green. And the green subject reflects green beams, absorbing, red and dark blue.
If to mix paints of different colour everyone will absorb to (clean) various components of this world, the mix will become more dark. Thus, mixing of paints is the process opposite to mixing of colour beams. To receive certain colour gamut, it is necessary to use other set of primary colours. The primary colours used in painting, are called as the basic pigmentary colours. It is purple, or "шфхрыіэю ъЁрёэ№щ" dark blue and yellow, usually (but it is wrong) named red, dark blue and yellow. Black add to increase density of dark sites, and the sated mix of all primary colours nevertheless reflects to some extent light. As a result instead of black colour it turns out dark brown.
Waves and particles
In a XVII-th century Isaak Newton and other scientists believed that light consists of quickly moving particles which named corpuscles. The Danish scientist Hristian Gjujgens asserted that light consists of waves.
In 1801 English scientist Thomas Young has made a number of experiences with light diffraction. This phenomenon consists that at passage through very narrow crack light slightly dissipates, instead of extends as the crow flies. Young has explained diffraction by distribution of light in the form of waves. And in 1860th the Scottish scientist James Clark Maksvell has come out with the assumption that electromagnetic energy extends waves, and that light is a special kind of this energy.
However to the XX-th century beginning German scientist Max Planck in the works has proved that energy of radiation can exist only in the form of tiny clots - quanta. This proof underlies Planck's quantum theory for which it in 1918 has received the Nobel Prize in physics area. The quantum of light radiation is the particle named a photon. At radiation or absorption light always behaves as a stream of photons. Thus, sometimes light behaves as a wave, sometimes - as particles. Therefore it is considered that it has the dual nature. Scientists, explaining the data of supervision, can use either the wave theory, or the theory of particles.
Like an electric current, light can be generated by other kinds of energy. The sun generates light and other electromagnetic radiations by powerful reactions of synthesis in which process hydrogen turns to helium. At coal or tree combustion chemical energy of fuel turns to heat and light. Current passage through a thin incandescent filament in an electric bulb yields the same result. The fluorescent lamp works by other principle. On the ends of the tube filled with steams (usually mercury) under the big pressure, the high voltage moves. Steam starts to be shone, letting out ultra-violet radiation which operates on a chemical covering of internal walls of a tube. The covering absorbs invisible ultra-violet radiation and itself radiates energy of light. This process of transformation of radiation is called as fluorescence. The phosphorescence - the phenomenon of the same sort, but a luminescence thus proceeds long enough and after removal of a source of radiation. The shone paint phosphoresces. After short-term influence on it of bright light it is shone by hours. Fluorescence and a phosphorescence are luminescence forms - radiations of light without heat influence.
Some live organisms, including the bugs-svetljakov, separate kinds of fishes, mushrooms and bacteria, generate light in the way of a bioluminescence. In this case a light source is the chemical energy received at oxidation of substance, named ljutsiferinom.
One of the most useful light sources is the laser. This word is made of the first letters of the full term "ѕёшыхэшх light by a method induced шчыѕёхэш " (in English light amplification by stimulated emission of radiation). In a laser tube under the influence of an electricity from atoms photons are liberated.
Laser light is coherent. It means that the let out light waves rise and fall together. Light radiation of a high orientation received thus and the big density of energy has various scopes, including sewing together of fabrics in surgery, rezku steels, prompting of rockets on the purposes, an information transfer.