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Light and color in nature. Light and color: the basics. Light refraction and dispersion

Kotov Pavel, student 11 A class MBOU "Secondary School No. 11" IMRSC

The article - message presents a description of interesting natural phenomena associated with the refraction of light
, which was prepared for the lesson.

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LIGHT AND COLOR IN NATURE

Publication:

Work of a student of grade 11 - A

MBOU "Secondary School No. 11"

Kotova Pavel

Message for the lesson, presentation, video clip on the topic

Introduction

On the topic proposed by the teacher, I found so many interesting things for me, so many unexpected things, for example, about"Broken Ghost" which I had never even heard of before, that I decided to tell my classmates about everything, without repetition, in class. The presentation does not reflect the beauty of the phenomena that amazed me and which are explained by the understandable laws of physics, so I selected several interesting video clips to accompany my message.

Such a spectacle left no one indifferent! I think that not only I, but also others swore to themselves that they would see these natural phenomena and I would become that happy person who would see all this with my own eyes! For some, their whole life will pass, and they will not see anything like this with their own eyes, unaware of the beautiful, amazing world in which they live.

And now a little theory, which I considered necessary to provide to my classmates. I have kept all references from the original source in the text.

Theoretical minimum

The possibility of light decomposition was first discovered by Isaac Newton. A narrow beam of light, passed through a glass prism, was refracted and formed a multi-colored stripe on the wall - a spectrum.

Based on color characteristics, the spectrum can be divided into two parts. One part includes red, orange, yellow and yellow-green colors, the other - green, blue, indigo and violet.

The wavelengths of the visible spectrum rays are different - from 380 to 760 mmk . Beyond the visible part of the spectrum is the invisible part. Parts of the spectrum with wavelengths greater than 780 mmk called infrared, or thermal. They are easily detected by a thermometer installed in this part of the spectrum. Parts of the spectrum with wavelengths less than 380 mmk called ultraviolet


Rice. 1. Spectral decomposition of a color beam

Light rays emanating from different light sources have different spectral composition and therefore differ significantly in color. The light of an ordinary electric light bulb is yellower than sunlight, and the light of a stearin or paraffin candle or kerosene lamp is yellower than the light of an electric light bulb. This is explained by the fact that in the spectrum of a daylight beam, waves corresponding to blue color predominate, and in the spectrum of a beam from an electric light bulb with a tungsten and especially a carbon filament, red and orange color waves predominate. Therefore, the same object can take on different colors depending on what light source it is illuminated with.

As a result, bodies take on different color shades in natural and artificial light.

The color of each object depends on its physical properties, that is, its ability to reflect, absorb or transmit light rays. Therefore, rays of light incident on a surface are divided into reflected, absorbed and transmitted.

Bodies that almost completely reflect or absorb light rays are perceived as opaque.

Bodies that transmit a significant amount of light are perceived as transparent (glass).

If a surface or body reflects or transmits to the same extent all rays of the visible part of the spectrum, then such reflection or penetration of the light flux is called non-selective.

Thus, an object appears black if it absorbs almost all the rays of the spectrum equally, and white if it completely reflects them.

If we look at objects through clear glass, we will see their true color. Consequently, colorless glass almost completely transmits all the color rays of the spectrum, except for a small amount of reflected and absorbed light, which also consists of all the color rays of the spectrum.

If you take a blue filter, then all objects behind the glass will appear blue, since blue glass transmits mainly blue rays of the spectrum, and almost completely absorbs rays of other colors.

The color of an opaque object also depends on its reflection and absorption of waves of different spectral composition. So, an object appears blue if it reflects only blue rays and absorbs all the rest. If an object reflects red rays and absorbs all other rays of the spectrum, it appears red.

There is no material in nature that reflects or absorbs 100% of the light falling on it, so there is neither perfect white nor perfect black. The whitest color is a powder of chemically pure barium sulfate, pressed into a tile, which reflects 94% of the light incident on it. Zinc white is somewhat darker than barium sulfate; lead white, gypsum, lithoponic white, premium writing paper, chalk, etc. are even darker. The darkest surface is black velvet, reflecting about 0.2% of light.

Mixing colors.The perception of the colors that we see around us is caused by the action on the eye of a complex color stream consisting of light waves of different lengths. But we do not get the impression of variegation and multicolor, since the eye has the ability to mix various colors. Colors located close to each other, viewed from a great distance, seem to merge into one total color on the retina of our eye. This type of color mixing is called subjunctive or additive.

Rice. 2. Color wheel of complementary colors: 1 - large interval, 2 - medium interval, 3 - small interval

In this circle, the complementary color to red is bluish-green, to orange - blue, to yellow - blue, to yellow-green - violet. In any pair of complementary colors, one always belongs to the group of warm tones, the other to the group of cool tones.

When mechanically mixing paints, what is obtained is not the optical addition of colored rays on the retina of the eye, but the subtraction from the white ray illuminating our color mixture of those rays that are absorbed by the colored particles of paints. So, for example, when illuminated by a white beam of light on an object painted with a colored mixture of blue and yellow pigments, blue particles of Prussian blue will absorb red, orange and yellow rays, and yellow cadmium particles will absorb violet, blue and cyan rays. Green and similar bluish-green and yellow-green rays will remain unabsorbed, which, reflected from the object, will be perceived by the retina of our eye.

An example of subtractive color mixing is a ray of light passed through three glasses - yellow, cyan and magenta, which are placed one after the other and directed at a white screen. In places where two glasses overlap - magenta and yellow - you will get a red spot, yellow and cyan - green, cyan and magenta - blue. Where three colors overlap simultaneously, a black spot will appear.

Halo usually appears aroundSun or Moon , sometimes around other powerful, such as street lights. There are many types of halos and they are mainly caused by icecrystals V cirrus clouds at an altitude of 5-10 km in the upper layerstroposphere . The type of halo depends on the shape and arrangement of the crystals. The light reflected and refracted by ice crystals is often decomposed into a spectrum, which makes the halo look likerainbow .


Sun halo in the cityBryansk

Gloria ( lat. gloria - decoration; halo) is an optical phenomenon in clouds.

Observed on clouds located directly opposite the light source. The observer must be on the mountain or in the air, and the light source (Sun or Moon ) - behind his back.

Represents colored rings of light on a cloud around the observer's shadow. There is a bluish ring inside, a reddish outside, then the rings can be repeated with less intensity

Gloria explains herselfdiffraction light previously reflected in droplets of a cloud so that it returns from the cloud in the same direction in which it fell, that is, to the observer.


Effect "Broken Ghost" with a person's shadow, photo onKorzhenevskaya peak , Pamir

The Brocken Ghost appears when the Sun shines from behind a climber looking down from a ridge or peak into the fog. The climber's shadow moves through the fog, often taking on bizarre angular shapes caused by perspective. Apparent increase in shadow size -optical illusion , explained by the fact that the observer compares his shadow, lying on relatively close clouds, with distant surface objects visible through gaps in the clouds; or when it is impossible to navigate in the fog and measure sizes. In addition, shadows fall on drops of water located at different distances from the eye, which disruptsdepth perception .

The Brocken ghost is often surrounded by glowing rings of different colors -Gloria . They appear directly opposite the Sun when sunlight reflects off clouds made of equally sized water droplets. The effect is due todiffraction of light .

Rainbows occur because the sunlight refracted And reflected droplets water ( rain or fog ), floating in atmosphere . These droplets deflect light differently from differentcolors (refractive index There is less water for longer wavelength (red) light than for short wavelength (violet), so red light is deflected the weakest - by 137°30’, and violet light the most strongly - by 139°20’). As a resultwhite light decomposes intorange (happens

living organism.

    Color perception is the body's reaction to a light stimulus.

    The light rays visible and felt by humans constitute only a small octave, ranging from 400 to 700 nanometers (or millimicrons) in the range of oscillations of electromagnetic waves, which successively include: cosmic rays, radioactive rays, X-rays, ultraviolet rays, light rays (visible light ), infrared rays, ultrashort, short, medium and long radio waves.

    The visible spectrum of rays includes colors ranging from violet to red through blue, green, yellow and orange.

    In nature, there are natural series of color development from white (sprout) through the visible color spectrum to black (rot). Nature itself puts colors in a certain series.

    The Earth's atmosphere envelops us and creates an amazing environment that bears color.

    The human body, being a part of nature, reacts sensitively to light and color and has an individual, unique scale of color perception.

    Color rays bypass vision and act on the human nervous system; red color increases blood circulation, and blue color stops inflammatory processes.

    The human eye is a unique optical system that gives us the ability to distinguish the size, shape, texture, shine, transparency, flicker and color of objects.

    The nature of light is such that all dark tones are at the bottom and light tones are at the top, which is a consequence of gravity.

    In normal lighting, our eyes see through “cones,” and in low light, through “rods.” Rods give us the impression of light, and cones give us color.

    In the animal world, the presence of cones and rods is distributed differently. For example, chickens have only cones and they sleep when the sun goes down, while owls, on the contrary, have only rods and do not see during the daytime.

    In the human eye, only cones are located in the center of the retina, in the area of ​​the fovea. Their density is very high. There are 50,000 cones in an area of ​​1 mm2. It is this center that is mainly responsible for measuring color in our eye.

    With twilight vision, both cones and rods are involved in the work of the eye, due to this there is a sharp shift in the perception of color and it is impossible to give an accurate description of color.

    In living nature, color and light are a product of the vital activity of the organism in the process of its functioning.

    The glow of organisms (bioluminescence) has a specific purpose: in jellyfish it is a reaction to mechanical irritation, in bottom-dwelling “polychaete” worms it is a signal during the breeding season, squid and shrimp eject luminous mucus, using it as a light curtain.

    In addition to glands with photogenic cells that produce light, deep-sea animals have special luminous organs - “photophores”. Sometimes photophores are equipped with light filters and the animal glows rainbowly.

    In living organisms, almost all biochemical energy is converted into light during oxidation, whereas in a conventional incandescent lamp 70% of the energy is spent on the formation of heat, therefore the creation of artificial living light is one of the promising areas of bionics.

    Under the influence of solar energy, the process of photosynthesis occurs in the leaves of plants, i.e. the process of formation of organic substances (sugars and carbohydrates) from inorganic substances (water, carbon dioxide and mineral salts) obtained from the external environment.

    To better capture daylight by plants, various leaf arrangements have been created in nature. This is regular, whorled, mosaic, spiral, etc.

    Nature has endowed many animals with the ability to camouflage - change their external color. This allows animals to best adapt in the fight for survival.

    Color change in animals is a complex biological process that occurs under the influence of external stimuli, mainly through vision. Under the skin of the animal there are special elastic cells called “chromatophores” filled with a dye. At the signal from the animal, some chromatophores stretch and others contract, resulting in a change in the color of the skin.

    Under the chromatophores lie other cells - “iridocysts”, filled with a number of mirrors and a system of prisms that refract and decompose light, due to which the skin of animals acquires a special metallic sheen.

    In design, colors are generally accepted to provide security and orderliness in color symbolism.

Yellow color is a warning color, meaning “attention”.

Orange color - means attention, “danger”.

Red color is fire-fighting, “forbidding.”

Green color is permissive, “free”.

Blue color is prescriptive, explanatory.

White color - direction of movement, “free”.

    According to their psychological impact on a person, colors are divided into:

A) Stimulating (warm colors), promoting excitement and acting as irritants - red, carmine, cinnabar, orange, yellow.

B) Disintegrating (cold colors), muting irritation - violet, blue, light blue, blue-green.

C) Pastels (soft colors), muting pure colors.

D) Static (balanced colors), distracting from exciting colors - green, olive, yellow-green, purple.

E) Colors of dull tones that do not cause irritation and help concentration - based on gray, white and black.

E) Warm dark colors, stabilizing irritation and acting sluggishly and inertly - ocher, brown earths, dark brown.

G) Cold dark colors, isolating and suppressing irritation - dark gray, black-blue, dark blue, dark green.

The fact that color is an electromagnetic wave perceived by the human eye and the visible part of the spectrum, I. Newton described in the work “Optics”. Despite the fact that long before this, the English philosopher and natural scientist Roger Bacon also observed the optical spectrum in a glass of water; the first explanation of visible radiation was given by I. Newton. Similar attempts at color research were carried out a little later Johann Goethe in the work “The Theory of Colors”, in the 18th century, in Russia, by M. V. Lomonosov.

I. Newton managed to decompose white light into the colors of the spectrum, which was the first significant breakthrough in the study of color.

The scientist’s main prerequisite for the discovery of the spectrum was the desire to improve lenses for telescopes: the main disadvantage of telescopic images was the presence of rainbow-colored edges.

In 1666, in Cambridge, he carried out an experiment in decomposing white color with a prism: through a small round hole in the window shutter, a beam of light penetrated into a darkened room, and in its path a glass trihedral prism appeared, in which the beam of light refracted. A multi-colored strip appeared on the screen behind the prism, later called the spectrum. He determined that a ray of white daylight consists of rays of different colors, namely: red, orange, yellow, green, blue (cyan), indigo and deep violet.

Newton I. Optics or treatise on reflections, refractions, bendings and colors of light. - M.: State Publishing House of Technical and Theoretical Literature, 1954.

He explained that their mixing is the main reason for the variety of color harmonies and the richness of nature's colors.

He also discovered that a colored ray, reflected and refracted an infinite number of times, remains the same color, which meant that color is a certain stable characteristic. He also noticed that when white light is added to a colored ray, it becomes more complex, causing the color to become rarefied and weaker until it disappears completely, forming gray or white. Thus, the more complex the color, the less full and intense it is.

I. Newton also established that it is possible, on the contrary, by mixing the seven colors of the spectrum, to again obtain white. To do this, he placed in the path of the colored beam (spectrum) decomposed by the prism a biconvex lens, which again superimposes different colors one on top of the other; converging, they form a white spot on the screen. If you place a narrow opaque strip in front of the lens (in the path of colored rays) to block any part of the spectrum, then the spot on the screen will become colored.

The scientist also determined the refractive index of rays of different colors. For this purpose, a hole was cut in the screen; By moving the screen, it was possible to release a narrow beam of rays of one color or another through the hole. Such a selected beam, refracted in the second prism, was no longer stretched into a strip: it corresponds to a certain refractive index, the value of which depends on the color of the selected beam. The dependence of the refractive index on color is called “color dispersion” (from the Latin dispergo - scatter).

Studying the nature of light and color, Newton came to the conclusion that the constant colors of natural bodies occur due to the fact that some bodies reflect certain types of rays, other bodies reflect other types more abundantly than others 1. Colored powders, as Newton noted, suppress and retain a very significant part of the light with which they are illuminated. And they become colored, reflecting the light of their own color most abundantly 2. Newton I. Optics or a treatise on the battles, refractions, bendings and colors of light. - M.: State Publishing House of Technical and Theoretical Literature, 1954. - 367 p.

It must be said that, despite further research, this theory (the corpuscular theory of light) cannot be considered incorrect, because color can really be considered as a stream of photons - elementary massless particles moving at the speed of light and having an electric charge equal to zero. The photon, as a quantum particle, is characterized by wave-particle duality, that is, the manifestation of the properties of a particle and a wave at the same time. It is not possible to call I. Newton an opponent of the wave theory: he did not reject this idea. Newton drew an analogy between color and sound, believing that both of these phenomena were of a similar nature, which probably anticipated the discovery of the electromagnetic nature of sound and light. “Just as the sound of a bell, or a musical string, or other sounding bodies is nothing more than an oscillating movement, and in the air from an object nothing other than this movement spreads... in the latter the sensations of these movements appear in the form of flowers.”

On the other hand, in a treatise presented to the Royal Society in 1675, he writes that light cannot be simply vibrations of the ether, since then it could, for example, propagate through a curved pipe, as sound does. But he also suggests that the propagation of light excites vibrations in the ether, which gives rise to diffraction and other wave effects.

In the 18th century in Russia, M. V. Lomonosov exploring the problems of color phenomena and makes a number of important discoveries that are not widely known. He discovered that light consists of three ethers, which flow from the sun and luminous bodies like a river. Ethers have three types of movement, which he called incessant, unsteady and rotating. Ether streams consist of three types of particles of different sizes. Of these, salt particles make up the red ether, mercury particles make up the yellow ether, and sulfur particles make up the blue ether. The remaining colors are formed by mixing red, yellow and blue. Ethereal particles adhere to suitable particles on the surface of objects and cause them to vibrate with varying intensity. Part of the movement is thus transmitted, and the remaining movement determines the color we see. If the surface of an object has absorbed the rotating or rotating movement of ethereal particles, the eye sees a black color.

So Lomonosov discovered the physical and chemical nature of color .

According to this theory, temperature affects the intensity of the paint, which he proved experimentally. The human eye perceives color due to the fact that the movement of etheric particles, not absorbed by the object, produces a corresponding movement at the bottom of the eye.

As the wave theory of light developed, it was clarified that each color corresponds to a certain frequency of the light wave. English scientist T. Jung, who developed in 1800 wave theory of interference based on his formulation wave superposition principle. Based on the results of his experiments, he quite accurately estimated the wavelength of light in various color ranges.

According to the principle of interference (nonlinear addition of the intensities of several light waves), darkness can be obtained by adding light with light, that is, mutually extinguishing light. Young explored various applications of the interference principle and came to the conclusion that light must travel in wave motion. It turned out to be completely impossible to explain the interference bands from the point of view of outflow. He also calculated the average wavelength of light of different colors. Thomas Young suggested that the colors correspond to waves of different lengths, with red rays having the longest waves and violet ones the shortest.

With the development of quantum mechanics, the idea became established Louis de Broglie about wave-particle duality, according to which light must simultaneously have wave properties, which explains its ability to diffraction and interference, and corpuscular properties, which explain its absorption and emission.

For full understanding essences of color let's turn to concept of electromagnetic radiation , that is, to a disturbance of the electromagnetic field propagating in space. Electromagnetic radiation is usually divided into frequency ranges, between which there are no sharp transitions - the boundaries are arbitrary. Figure 2 shows the full spectrum of electromagnetic radiation, graduated by decreasing frequency: radio waves (starting with ultra-long ones), infrared radiation, visible light, ultraviolet, x-ray and gamma radiation.

Figure 2 - Full spectrum of electromagnetic radiation

In the general spectrum of electromagnetic radiation visible radiation constitutes a very small percentage.

When composing a bouquet, you need to pay attention not only to the set of flowers and decorative elements, the meaning of the flower, but also to how it will look in different lighting and how the color scheme affects a person.

I. Newton in 1666, using a sunbeam and a prism, determined the color spectrum. Red, orange, yellow, green, blue, indigo and violet are the colors that make up white light. In other words, light is the region of electromagnetic radiation (electromagnetic energy) visible to the human eye. As we know from school, radiation comes from the main source - the Sun and is divided into infrared, ultraviolet and visible waves. The last type of radiation is the white light that we see.

Newton's color spectrum

Starting from ancient Greek scientists, people have tried to find the answer to the questions “what is light?”, “where does it come from?” and “how does it spread?” In our time, when scientists have much more opportunities than Newton and others, science talks about the duality of the nature of light. Penetrating through a hole, it behaves like a wave, and when it hits, for example, a metal surface, it behaves like a particle - a photon - bombarding this surface.

Light waves

A wave is understood as the part of an oscillation that has translational motion. They can be refracted differently and cause different color sensations. It depends on their length.

The flow of light, upon reaching the surface of the body, is divided into three parts: reflected, transmitted and absorbed.

Bodies can be transparent or opaque. Only transparent bodies tend to reflect, absorb and transmit light through themselves. We determine the color of an object after our eye detects the interaction of light and the object, which depends on the wavelength of the reflected light. A white sheet is white because it reflects all colors, green will reflect mainly green colors, blue will reflect blue, etc. If an object absorbs all colors, then it is perceived by the eye as black.

Some of the violet, blue, cyan rays are retained and scattered by the air. As a result, we see blue skies and pink snow on the mountain tops.

Reflection can be specular (the angle of reflection of the beam is the same as that of incidence) and diffusion, in which the beam of reflection can be different. The surfaces with which a person comes into contact reflect the rays partly specularly and partly by diffusion. Shiny and glossy surfaces give a clear mirror reflection of color, while matte and rough surfaces are characterized by diffusion. That is why the eye sees a less clearly displayed light source.

Sources of light

Natural

Natural. The Sun and other components of the Cosmos. But we see the glow of planets, stars and the Moon distorted due to the atmosphere.

Artificial

Artificial. These include various types of lamps, lasers, etc. When an object is illuminated with a conventional incandescent lamp, it acquires a warm yellowish tint (the tungsten filament heats up to a yellow color). The use of fluorescent lamps is known for their cool glow (they emit predominantly ultraviolet light, and the visible spectrum consists of violet, blue and green, and there is very little thermal radiation). Halogen lamps also consist of a tungsten filament, a pair of halogens that are not in a vacuum (unlike the outdated Ilyich light bulbs). Colors in this lighting become brighter, richer, and more cheerful.

Laser

The most useful piece of light source is a laser. In a laser tube, photons are released from atoms under the influence of electricity. They fly out of it in the form of a narrow beam of light or some other form of electromagnetic radiation. It depends on the substance that is used to produce photons.

Every day a person is faced with many environmental factors that affect him. One such factor that has a strong influence is color. It is known that color can be seen by a person only in light; in the dark we do not see any colors. Light waves are perceived by the human eye. We see objects because they reflect light and because our eye is able to perceive these reflected rays. Rays of solar or electric light - light waves in the human visual apparatus are converted into sensation. This transformation occurs in three stages: physical, physiological, psychological.

Physical– light emission; physiological– the effect of color on the eye and its transformation into nerve impulses going to the human brain; psychological– color perception.

The physical stage of the formation of visual perception consists in the transformation of the energy of visible radiation by various media into the energy of a modified radiation flux and is studied by physics.

Visible radiation is called light. Light is the visible part of the electromagnetic spectrum; it is a special case of electromagnetic radiation . Physicists joke that light is the darkest place in physics. Light has a dual nature: when it propagates, it behaves like a wave, and when absorbed and emitted, it behaves like a stream of particles. So, light belongs to space, and color belongs to the object. Color is a sensation that occurs in the human organ of vision when exposed to light. .

In color science, it is customary to consider light as electromagnetic wave motion. In the region of visible radiation, each wavelength corresponds to the sensation of a color.

There are seven primary colors in the spectrum of white sunlight: red, orange, yellow, green, blue, indigo, and violet. The average observer's eye can distinguish about 120 colors in the spectrum of white light. For the convenience of designating colors, it is customary to divide the optical radiation spectrum into three zones:

Long wavelength - from red to orange;

Medium wave - from orange to blue;

Short wavelength - from blue to violet.

This division is justified by the qualitative differences between the colors included in different areas of the spectrum. Each color of the spectrum is characterized by its own wavelength (Table 1), i.e. it can be precisely specified by the wavelength or vibration frequency. The shortest waves are violet, the longest are red. Light waves themselves have no color. Color appears only when these waves are perceived by the human visual apparatus.

The eye can perceive waves with a length of 400 to 700 nanometers (a nanometer is one billionth of a meter, a unit of measurement for the length of light waves).

Table 1. Correspondence of wavelength ranges to color sensations

On both sides of the visible part of the spectrum there are ultraviolet and infrared regions, which are not perceived by the human eye, but can be detected by special equipment (Table 2). Night vision cameras operate using infrared radiation, and ultraviolet radiation, although invisible to the human eye, can cause significant damage to vision. The speed of propagation of all types of waves of electromagnetic oscillations is approximately 300,000 km/s.

Table 2. Types of electromagnetic radiation

Light waves enter the retina of the eye, where they are perceived by light-sensitive receptors that transmit signals to the brain, and there the sensation of color is formed. This sensation depends on the wavelength and intensity of the radiation. And all the objects that surround us can either emit light (color), or reflect or transmit the light falling on them partially or completely.

For example, if grass is green, this means that out of the entire range of waves, it reflects mainly the waves of the green part of the spectrum, and absorbs the rest. When we say “this cup is red,” what we really mean is that it absorbs all light rays except red ones. The cup itself has no color; color is created by lighting it. Thus, the red cup reflects mainly the waves of the red part of the spectrum. If we say that an object has a color, it means that in fact this object (or its surface) has the property of reflecting waves of a certain length, and the reflected light is perceived as the color of the object. If an object completely blocks the incident light, it will appear black to us, and if it reflects all the incident rays, it will appear white. True, the last statement will be true only if the light is white, uncolored. If the light acquires any shade, then the reflecting surface will have the same shade. This can be observed at sunset, which colors everything around with crimson tones, or on a twilight winter evening, when the snow appears blue. The experiment with the use of colored color is described quite curiously by I. Itten in his book “The Art of Color”.

How the visual apparatus recognizes these waves is still not completely known. All we know is that different colors result from quantitative differences in light sensitivity.

In this context, it would be logical to recall another definition of color. Color is a different number of vibrations of light waves from a given light source, perceived by our eye in the form of certain sensations, which we call color .

The sensation of color is created when waves of a certain length predominate in the color. But if the intensity of all waves is the same, then the color is perceived as white or gray. An object that does not emit waves is perceived as black. In this regard, all visual sensations of color are divided into two groups: chromatic and achromatic.

White, black and all gray colors are called achromatic.. Their spectrum includes rays of all wavelengths equally. If there is a predominance of one wavelength, then this color becomes chromatic. Chromatic colors include all spectral and other natural colors. .

2.2. Basic color characteristics

To unambiguously define (specificate) color, a system of psychophysical characteristics is often used. These include the following characteristics:

Color tone,

Lightness;

Saturation.

Color tone - the quality of a color that allows it to be named (for example, red, blue, etc.) . Interestingly, the untrained eye can distinguish up to 180 color tones in bright daylight, while the developed human eye can distinguish about 360 shades of color. Achromatic colors have no hue.

Lightness is the degree to which a given color differs from black.. In spectral colors, yellow is the lightest color and violet is the darkest. Within one color tone, the degree of lightness depends on the use of white. Lightness is a degree inherent in both chromatic and achromatic colors . Shades of the same color of different lightness are called monochrome .

Saturation is the degree of difference between a chromatic color and an achromatic color of equal lightness. So, if a pure spectral color, for example red, is taken as 100%, then when mixing 70% red and 30% white, the saturation of the resulting mixture will be 70%. The degree of color perception depends on saturation.

The colors of the spectrum are the most saturated, with the most saturated being violet and the least saturated being yellow.

Achromatic colors can be called colors of zero saturation.

A trained human eye can distinguish about 25 shades of color by saturation, from 65 shades by lightness in high light conditions and up to 20 shades in low light conditions.

Proper and non-proper qualities of color. Color, hue, lightness, saturation are called the intrinsic qualities of color. Own qualities are those qualities that are objectively inherent in him.

Improper qualities are not objectively inherent in flowers, but arise as a result of an emotional reaction when they are perceived. We say that colors are warm and cold, light and heavy, dull and sonorous, protruding and receding, soft and hard. These characteristics are important for the artist, since through them the expressiveness and emotional mood of the work are enhanced.

The change in the volume of the image depends on the color saturation (Fig. 1). Actively saturated colors make the image more voluminous than weakly saturated or darkened colors. Whitening and darkening not only reduce color activity, but also weaken color contrasts between spots. A monochrome image, just like a saturated one, is capable of actively conveying volume close to the achromatic version.

Rice. 1. Changing the volume of the image depending on color saturation:

a – optimally saturated colors; b – weakly saturated (lightened) colors; c – achromatic version; d – weakly saturated (darkened) colors; d – monochrome image of the object, relief, volume and emotional mood of the composition. When using weakly saturated colors (highlighted or darkened), the volume will be felt less than when using saturated colors.

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