Optical phenomena: examples in nature and interesting facts. Changes that occur with bodies are called physical phenomena. Physical phenomena are examples and attempts to explain them.

“Optical phenomena in nature”

1. Introduction

a) The concept of optics

b) Classification of optics

c) Optics in the development of modern physics

2. Phenomena associated with the reflection of light

4. Auroras

Introduction

Optics concept

The first ideas of ancient scientists about light were very naive. They thought that visual impressions arise when objects are felt with special thin tentacles that come out of the eyes. Optics was the science of vision, this is how this word can most accurately be translated.

Gradually in the Middle Ages, optics turned from the science of vision into the science of light, facilitated by the invention of lenses and the camera obscura. At the present time, optics is a branch of physics that studies the emission of light and its propagation in various media, as well as its interaction with matter. Issues related to vision, the structure and functioning of the eye, became a separate scientific field - physiological optics.

Optics classification

Light rays are geometric lines along which light energy propagates; when considering many optical phenomena, you can use the idea of ​​them. In this case, we talk about geometric (ray) optics. Geometric optics has become widespread in lighting engineering, as well as when considering the actions of numerous instruments and devices - from magnifying glasses and glasses to the most complex optical telescopes and microscopes.

Intensive research into the previously discovered phenomena of interference, diffraction and polarization of light began in early XIX century. These processes were not explained within the framework of geometric optics, so it was necessary to consider light in the form of transverse waves. As a result, wave optics appeared. Initially, it was believed that light is elastic waves in a certain medium (world ether) filling the world space.

But the English physicist James Maxwell in 1864 created the electromagnetic theory of light, according to which light waves are electromagnetic waves with a corresponding range of lengths.

And already at the beginning of the 20th century, new studies showed that in order to explain some phenomena, for example the photoelectric effect, there is a need to represent a light beam in the form of a stream of peculiar particles - light quanta. Isaac Newton had a similar view on the nature of light 200 years ago in his “theory of the effusion of light.” Now quantum optics is doing this.

The role of optics in the development of modern physics.

Optics also played a significant role in the development of modern physics. The emergence of two of the most important and revolutionary theories of the twentieth century (quantum mechanics and the theory of relativity) is connected in principle with optical research. Optical methods for analyzing matter at the molecular level have given rise to a special scientific field - molecular optics, which also includes optical spectroscopy, used in modern materials science, plasma research, and astrophysics. There are also electron and neutron optics.

On modern stage development, an electron microscope and a neutron mirror were created, optical models of atomic nuclei were developed.

Optics, influencing the development of various areas of modern physics, is itself today in a period of rapid development. The main impetus for this development was the invention of lasers - intense sources of coherent light. As a result, wave optics rose to a higher level, the level of coherent optics.

Thanks to the advent of lasers, many scientific and technical developing areas have emerged. Among which are nonlinear optics, holography, radio optics, picosecond optics, adaptive optics, etc.

Radio optics originated at the intersection of radio engineering and optics and deals with the study of optical methods for transmitting and processing information. These methods are combined with traditional electronic methods; The result was a scientific and technical direction called optoelectronics.

The subject of fiber optics is the transmission of light signals through dielectric fibers. Using the achievements of nonlinear optics, it is possible to change the wavefront of a light beam, which is modified as light propagates in a particular medium, for example, in the atmosphere or in water. Consequently, adaptive optics has emerged and is being intensively developed. Closely related to this is photoenergetics, which is emerging before our eyes and deals, in particular, with the issues of efficient transmission of light energy along a beam of light. Modern laser technology makes it possible to produce light pulses with a duration of only picoseconds. Such pulses turn out to be a unique “tool” for studying a number of fast processes in matter, and in particular in biological structures. A special direction has emerged and is developing - picosecond optics; Photobiology is closely related to it. It can be said without exaggeration that the widespread practical use of the achievements of modern optics is a prerequisite for scientific and technological progress. Optics opened the way to the microcosm for the human mind, and it also allowed it to penetrate the secrets of the stellar worlds. Optics covers all aspects of our practice.

Phenomena associated with the reflection of light.

The object and its reflection

The fact that the landscape reflected in still water does not differ from the real one, but is only turned upside down, is far from true.

If a person looks late in the evening at how lamps are reflected in the water or how the shore descending to the water is reflected, then the reflection will seem shortened to him and will completely “disappear” if the observer is high above the surface of the water. Also, you can never see the reflection of the top of a stone, part of which is immersed in water.

The landscape appears to the observer as if it were viewed from a point located as much below the surface of the water as the observer's eye is above the surface. The difference between the landscape and its image decreases as the eye approaches the surface of the water, and also as the object moves away.

People often think that the reflection of bushes and trees in a pond has brighter colors and richer tones. This feature can also be noticed by observing the reflection of objects in a mirror. Here psychological perception plays a greater role than the physical side of the phenomenon. The frame of the mirror and the banks of the pond limit a small area of ​​the landscape, protecting a person’s lateral vision from excess scattered light coming from the entire sky and blinding the observer, that is, he looks at a small area of ​​the landscape as if through a dark narrow pipe. Reducing the brightness of reflected light compared to direct light makes it easier for people to observe the sky, clouds and other brightly lit objects that, when directly observed, are too bright for the eye.

Dependence of reflection coefficient on the angle of incidence of light.

At the boundary of two transparent media, light is partially reflected, partially passes into another medium and is refracted, and partially absorbed by the medium. The ratio of reflected energy to incident energy is called the reflection coefficient. The ratio of the energy of light transmitted through a substance to the energy of incident light is called transmittance.

Reflection and transmittance coefficients depend on the optical properties, the adjacent media and the angle of incidence of light. So, if light falls on a glass plate perpendicularly (angle of incidence α = 0), then only 5% of the light energy is reflected, and 95% passes through the interface. As the angle of incidence increases, the fraction of reflected energy increases. At the angle of incidence α=90˚ it is equal to unity.

The dependence of the intensity of light reflected and transmitted through a glass plate can be traced by placing the plate at different angles to the light rays and assessing the intensity by eye.

It is also interesting to evaluate by eye the intensity of light reflected from the surface of a reservoir, depending on the angle of incidence, to observe the reflection of the sun's rays from the windows of a house at different angles of incidence during the day, at sunset, and at sunrise.

Safety glass

Conventional window glass partially transmits heat rays. This is good for use in northern areas, as well as for greenhouses. In the south, the rooms become so overheated that it is difficult to work in them. Protection from the Sun comes down to either shading the building with trees, or choosing a favorable orientation of the building during reconstruction. Both are sometimes difficult and not always feasible.

To prevent glass from transmitting heat rays, it is coated with thin transparent films of metal oxides. Thus, a tin-antimony film does not transmit more than half of thermal rays, and coatings containing iron oxide completely reflect ultraviolet rays and 35-55% of thermal rays.

Solutions of film-forming salts are applied from a spray bottle to the hot surface of the glass during its heat treatment or molding. At high temperatures, salts turn into oxides, tightly bound to the surface of the glass.

Glasses for sunglasses are made in a similar way.

Total internal reflection of light

A beautiful spectacle is the fountain, whose ejected jets are illuminated from within. This can be depicted under normal conditions by performing the following experiment (Fig. 1). In a tall tin can, drill a round hole at a height of 5 cm from the bottom ( A) with a diameter of 5-6 mm. The light bulb with the socket must be carefully wrapped in cellophane paper and placed opposite the hole. You need to pour water into the jar. Opening the hole A, we get a jet that will be illuminated from within. In a dark room it glows brightly and looks very impressive. The stream can be given any color by placing colored glass in the path of the light rays b. If you put your finger in the path of the stream, the water splashes and these droplets glow brightly.

The explanation for this phenomenon is quite simple. A ray of light passes along a stream of water and hits a curved surface at an angle greater than the limiting one, experiences total internal reflection, and then again hits the opposite side of the stream at an angle again greater than the limiting one. So the beam passes along the jet, bending along with it.

But if the light were completely reflected inside the jet, then it would not be visible from the outside. Part of the light is scattered by water, air bubbles and various impurities present in it, as well as due to the uneven surface of the jet, so it is visible from the outside.

Cylindrical light guide

If you direct a light beam at one end of a solid glass curved cylinder, you will notice that light will come out of its other end (Fig. 2); Almost no light comes out through the side surface of the cylinder. The passage of light through a glass cylinder is explained by the fact that, falling on the inner surface of the cylinder at an angle greater than the limiting one, the light undergoes complete reflection many times and reaches the end.

The thinner the cylinder, the more often the beam will be reflected and the larger part of the light will fall on the inner surface of the cylinder at angles greater than the limiting one.

Diamonds and gems

There is an exhibition of the Russian diamond fund in the Kremlin.

The light in the hall is slightly dimmed. The jewelers' creations sparkle in the windows. Here you can see such diamonds as “Orlov”, “Shah”, “Maria”, “Valentina Tereshkova”.

The secret of the wonderful play of light in diamonds is that this stone has a high refractive index (n=2.4173) and, as a result, a small angle of total internal reflection (α=24˚30′) and has greater dispersion, causing the decomposition of white light to simple colors.

In addition, the play of light in a diamond depends on the correctness of its cut. The facets of a diamond reflect light multiple times within the crystal. Due to the great transparency of high-class diamonds, the light inside them almost does not lose its energy, but only decomposes into simple colors, the rays of which then burst out in various, most unexpected directions. When you turn the stone, the colors emanating from the stone change, and it seems that it itself is the source of many bright multi-colored rays.

There are diamonds colored red, bluish and lilac. The shine of a diamond depends on its cut. If you look through a well-cut water-transparent diamond into the light, the stone appears completely opaque, and some of its facets appear simply black. This happens because the light, undergoing total internal reflection, comes out in the opposite direction or to the sides.

When viewed from the side of the light, the top cut shines with many colors and is shiny in places. The bright sparkle of the upper edges of a diamond is called diamond luster. The underside of the diamond appears to be silver-plated from the outside and has a metallic sheen.

The most transparent and large diamonds serve as decoration. Small diamonds are widely used in technology as a cutting or grinding tool for metalworking machines. Diamonds are used to reinforce the heads of drilling tools for drilling wells in hard rocks. This use of diamond is possible due to its great hardness. Other precious stones in most cases are crystals of aluminum oxide with an admixture of oxides of coloring elements - chromium (ruby), copper (emerald), manganese (amethyst). They are also distinguished by hardness, durability and have beautiful colors and “play of light”. Currently, they are able to artificially obtain large crystals of aluminum oxide and paint them in the desired color.

The phenomena of light dispersion are explained by the variety of colors of nature. A whole set of optical experiments with prisms was carried out by the English scientist Isaac Newton in the 17th century. These experiments showed that white light is not fundamental, it should be considered as composite (“inhomogeneous”); the main ones are various colors(“uniform” rays, or “monochromatic” rays). The decomposition of white light into different colors occurs because each color has its own degree of refraction. These conclusions made by Newton are consistent with modern scientific ideas.

Along with the dispersion of the refractive index, dispersion of the absorption, transmission and reflection coefficients of light is observed. This explains the various effects when illuminating bodies. For example, if there is some body transparent to light, for which the transmittance coefficient is large for red light and the reflection coefficient is small, but for green light it is the opposite: the transmittance coefficient is small and the reflection coefficient is large, then in transmitted light the body will appear red, and in reflected light it is green. Such properties are possessed, for example, by chlorophyll, a green substance found in plant leaves that causes green color. A solution of chlorophyll in alcohol appears red when viewed against light. In reflected light, the same solution appears green.

If a body has a high absorption coefficient and low transmittance and reflection coefficients, then such a body will appear black and opaque (for example, soot). A very white, opaque body (such as magnesium oxide) has a reflectance close to unity for all wavelengths, and very low transmittance and absorption coefficients. A body (glass) that is completely transparent to light has low reflection and absorption coefficients and a transmittance close to unity for all wavelengths. In colored glass, for some wavelengths the transmittance and reflection coefficients are practically equal to zero and, accordingly, the absorption coefficient for the same wavelengths is close to unity.

Phenomena associated with the refraction of light

Some types of mirages. From the larger variety of mirages, we will highlight several types: “lake” mirages, also called lower mirages, upper mirages, double and triple mirages, ultra-distant vision mirages.

Lower (“lake”) mirages appear above a very heated surface. Superior mirages, on the contrary, appear over a very cool surface, for example over cold water. If the lower mirages are observed, as a rule, in deserts and steppes, then the upper ones are observed in northern latitudes.

The upper mirages are diverse. In some cases they give a direct image, in other cases an inverted image appears in the air. Mirages can be double, when two images are observed, one simple and one inverted. These images may be separated by a strip of air (one may be above the horizon line, the other below it), but may directly merge with each other. Sometimes another one appears - a third image.

Ultra-long-range vision mirages are especially amazing. K. Flammarion in his book “Atmosphere” describes an example of such a mirage: “Based on the testimony of several trustworthy persons, I can report about a mirage that was seen in the city of Verviers (Belgium) in June 1815. One morning, residents of the city saw in the sky army, and it was so clear that one could distinguish the suits of the artillerymen and even, for example, a cannon with a broken wheel that was about to fall off... It was the morning of the Battle of Waterloo!” The described mirage is depicted in the form of a colored watercolor by one of the eyewitnesses. The distance from Waterloo to Verviers in a straight line is more than 100 km. There are known cases when similar mirages were observed at large distances - up to 1000 km. “The Flying Dutchman” should be attributed precisely to such mirages.

Explanation of the lower (“lake”) mirage. If the air near the surface of the earth is very hot and, therefore, its density is relatively low, then the refractive index at the surface will be less than in higher air layers. Changing the refractive index of air n with height h near the earth's surface for the case under consideration is shown in Figure 3, a.

In accordance with the established rule, light rays near the surface of the earth will in this case be bent so that their trajectory is convex downwards. Let there be an observer at point A. A light ray from a certain area of ​​​​the blue sky will enter the observer's eye, experiencing the specified curvature. This means that the observer will see the corresponding section of the sky not above the horizon line, but below it. It will seem to him that he sees water, although in fact there is an image of blue sky in front of him. If we imagine that there are hills, palm trees or other objects near the horizon line, then the observer will see them upside down, thanks to the noted curvature of the rays, and will perceive them as reflections of the corresponding objects in non-existent water. This is how an illusion arises, which is a “lake” mirage.

Simple superior mirages. It can be assumed that the air at the very surface of the earth or water is not heated, but, on the contrary, is noticeably cooled compared to higher air layers; the change in n with height h is shown in Figure 4, a. In the case under consideration, the light rays are bent so that their trajectory is convex upward. Therefore, now the observer can see objects hidden from him behind the horizon, and he will see them at the top, as if hanging above the horizon line. Therefore, such mirages are called upper.

The superior mirage can produce both an upright and an inverted image. The direct image shown in the figure occurs when the refractive index of air decreases relatively slowly with height. When the refractive index decreases rapidly, an inverted image is formed. This can be verified by considering a hypothetical case - the refractive index at a certain height h decreases abruptly (Fig. 5). The rays of an object, before reaching observer A, experience total internal reflection from the boundary BC, below which in this case there is denser air. It can be seen that the superior mirage gives an inverted image of the object. In reality, there is no abrupt boundary between the layers of air; the transition occurs gradually. But if it occurs sharply enough, then the superior mirage will give an inverted image (Fig. 5).

Double and triple mirages. If the refractive index of air changes first quickly and then slowly, then in this case the rays in region I will bend faster than in region II. As a result, two images appear (Fig. 6, 7). Light rays 1 propagating within the air region I form an inverted image of the object. Rays 2, which propagate mainly within region II, are bent to a lesser extent and form a straight image.

To understand how a triple mirage appears, you need to imagine three successive air regions: the first (near the surface), where the refractive index decreases slowly with height, the next, where the refractive index decreases quickly, and the third region, where the refractive index decreases again slowly. The figure shows the considered change in the refractive index with height. The figure shows how a triple mirage occurs. Rays 1 form the lower image of the object, they extend within the air region I. Rays 2 form an inverted image; I fall into air region II, these rays experience strong curvature. Rays 3 form the upper direct image of the object.

Ultra-long-range vision mirage. The nature of these mirages is least studied. It is clear that the atmosphere must be transparent, free of water vapor and pollution. But this is not enough. A stable layer of cooled air should form at a certain height above the earth's surface. Below and above this layer the air should be warmer. A light beam that gets inside a dense cold layer of air is, as it were, “locked” inside it and spreads through it as if along a kind of light guide. The beam path in Figure 8 is always convex towards less dense areas of air.

The occurrence of ultra-long-range mirages can be explained by the propagation of rays inside similar “light guides”, which nature sometimes creates.

Rainbow is a beautiful celestial phenomenon that has always attracted human attention. In former times, when people still knew little about the world around them, the rainbow was considered a “heavenly sign.” So, the ancient Greeks thought that the rainbow was the smile of the goddess Iris.

A rainbow is observed in the direction opposite to the Sun, against the background of rain clouds or rain. The multi-colored arc is usually located at a distance of 1-2 km from the observer, and sometimes it can be observed at a distance of 2-3 m against the background of water drops formed by fountains or water sprays.

The center of the rainbow is located on the continuation of the straight line connecting the Sun and the observer's eye - on the antisolar line. The angle between the direction towards the main rainbow and the anti-solar line is 41-42º (Fig. 9).

At the moment of sunrise, the antisolar point (point M) is on the horizon line and the rainbow has the appearance of a semicircle. As the Sun rises, the antisolar point moves below the horizon and the size of the rainbow decreases. It represents only part of a circle.

Often a secondary rainbow is observed, concentric with the first, with an angular radius of about 52º and an inverse arrangement of colors.

When the Sun's altitude is 41º, the main rainbow ceases to be visible and only part of the side rainbow protrudes above the horizon, and when the Sun's altitude is more than 52º, the side rainbow is not visible either. Therefore, in the middle equatorial latitudes at around noon this natural phenomenon is never observed.

The rainbow has seven primary colors, smoothly transitioning from one to another.

The type of arc, the brightness of the colors, and the width of the stripes depend on the size of the water droplets and their number. Large drops create a narrower rainbow, with sharply prominent colors, small drops create a blurry, faded and even white arc. That is why a bright narrow rainbow is visible in the summer after a thunderstorm, during which large drops fall.

The rainbow theory was first proposed in 1637 by Rene Descartes. He explained rainbows as a phenomenon related to the reflection and refraction of light in raindrops.

The formation of colors and their sequence were explained later, after unraveling the complex nature of white light and its dispersion in the medium. The diffraction theory of rainbows was developed by Erie and Partner.

We can consider the simplest case: let a beam of parallel solar rays fall on drops shaped like a ball (Fig. 10). A ray incident on the surface of a drop at point A is refracted inside it according to the law of refraction:

n sin α=n sin β, where n=1, n≈1.33 –

respectively, the refractive indices of air and water, α is the angle of incidence, and β is the angle of refraction of light.

Inside the drop, the ray AB travels in a straight line. At point B, the beam is partially refracted and partially reflected. It should be noted that the smaller the angle of incidence at point B, and therefore at point A, the lower the intensity of the reflected beam and the greater the intensity of the refracted beam.

Beam AB, after reflection at point B, occurs at an angle β`=β b and hits point C, where partial reflection and partial refraction of light also occurs. The refracted ray leaves the drop at an angle γ, and the reflected ray can travel further, to point D, etc. Thus, the light ray in the drop undergoes multiple reflection and refraction. With each reflection, some of the light rays come out and their intensity inside the drop decreases. The most intense of the rays emerging into the air is the ray emerging from the drop at point B. But it is difficult to observe it, since it is lost against the background of bright direct sunlight. The rays, refracted at point C, together create against the background dark cloud a primary rainbow, and rays refracted at point D give a secondary rainbow, which is less intense than the primary.

When considering the formation of a rainbow, one more phenomenon must be taken into account - the unequal refraction of light waves of different lengths, that is, light rays of different colors. This phenomenon is called dispersion. Due to dispersion, the angles of refraction γ and the angle of deflection Θ of rays in a drop are different for rays of different colors.

Most often we see one rainbow. There are often cases when two rainbow stripes appear simultaneously in the sky, located one after the other; They also observe an even larger number of celestial arcs - three, four and even five at the same time. This interesting phenomenon was observed by Leningraders on September 24, 1948, when in the afternoon four rainbows appeared among the clouds over the Neva. It turns out that rainbows can arise not only from direct rays; It often appears in the reflected rays of the Sun. This can be seen on the shores of sea bays, large rivers and lakes. Three or four rainbows - ordinary and reflected - sometimes create a beautiful picture. Since the rays of the Sun reflected from the water surface go from bottom to top, the rainbow formed in the rays can sometimes look completely unusual.

You should not think that rainbows can only be seen during the day. It also happens at night, although it is always weak. You can see such a rainbow after a night rain, when the Moon appears from behind the clouds.

Some semblance of a rainbow can be obtained through the following experiment: You need to illuminate a flask filled with water with sunlight or a lamp through a hole in a white board. Then a rainbow will become clearly visible on the board, and the angle of divergence of the rays compared to the initial direction will be about 41-42°. Under natural conditions, there is no screen; the image appears on the retina of the eye, and the eye projects this image onto the clouds.

If a rainbow appears in the evening before sunset, then a red rainbow is observed. In the last five or ten minutes before sunset, all the colors of the rainbow except red disappear, and it becomes very bright and visible even ten minutes after sunset.

A rainbow on the dew is a beautiful sight. It can be observed at sunrise on the grass covered with dew. This rainbow is shaped like a hyperbola.

Auroras

One of the most beautiful optical phenomena of nature is the aurora.

In most cases, auroras have a green or blue-green hue with occasional spots or a border of pink or red.

Auroras are observed in two main forms - in the form of ribbons and in the form of cloud-like spots. When the radiance is intense, it takes the form of ribbons. Losing intensity, it turns into spots. However, many tapes disappear before they have time to break into spots. The ribbons seem to hang in the dark space of the sky, resembling a giant curtain or drapery, usually stretching from east to west for thousands of kilometers. The height of this curtain is several hundred kilometers, the thickness does not exceed several hundred meters, and it is so delicate and transparent that the stars are visible through it. The lower edge of the curtain is quite sharply and clearly outlined and is often tinted in a red or pinkish color, reminiscent of a curtain border; the upper edge is gradually lost in height and this creates a particularly impressive impression of the depth of space.

There are four types of auroras:

A homogeneous arc - a luminous stripe has the simplest, calmest shape. It is brighter from below and gradually disappears upward against the background of the sky glow;

Radiant arc - the tape becomes somewhat more active and mobile, it forms small folds and streams;

Radial stripe - with increasing activity, larger folds overlap small ones;

As activity increases, the folds or loops expand to enormous sizes, and the bottom edge of the ribbon glows brightly with a pink glow. When activity subsides, the folds disappear and the tape returns to a uniform shape. This suggests that a homogeneous structure is the main form of the aurora, and folds are associated with increasing activity.

Radiances of a different type often appear. They cover the entire polar region and are very intense. They occur during an increase in solar activity. These auroras appear as a whitish-green cap. Such auroras are called squalls.

Based on the brightness of the aurora, they are divided into four classes, differing from each other by one order of magnitude (that is, 10 times). The first class includes auroras that are barely noticeable and approximately equal in brightness to the Milky Way, while the fourth class auroras illuminate the Earth as brightly as the full Moon.

It should be noted that the resulting aurora spreads to the west at a speed of 1 km/sec. The upper layers of the atmosphere in the area of ​​auroral flashes heat up and rush upward, which affected the increased braking of artificial Earth satellites passing through these zones.

During auroras, eddy electric currents arise in the Earth's atmosphere, covering large areas. They excite magnetic storms, the so-called additional unstable magnetic fields. When the atmosphere shines, it emits X-rays, which are most likely the result of the deceleration of electrons in the atmosphere.

Frequent flashes of radiance are almost always accompanied by sounds reminiscent of noise and crackling. Auroras have a great influence on strong changes in the ionosphere, which in turn affect radio communication conditions, i.e. radio communication is greatly deteriorated, resulting in severe interference, or even complete loss of reception.

The emergence of auroras.

The Earth is a huge magnet, the north pole of which is located near the south geographic pole, and the south pole is located near the north. And the Earth's magnetic field lines are geomagnetic lines emerging from the region adjacent to the Earth's north magnetic pole. They cover the entire globe and enter it in the region of the south magnetic pole, forming a toroidal lattice around the Earth.

It was believed for a long period of time that the location of magnetic field lines was symmetrical relative to the earth's axis. But in fact, it turned out that the so-called “solar wind,” i.e., a stream of protons and electrons emitted by the Sun, attacks the geomagnetic shell of the Earth from a height of about 20,000 km. It pulls it away from the Sun, thereby forming a kind of magnetic “tail” on the Earth.

Once in the Earth's magnetic field, an electron or proton moves in a spiral, winding around the geomagnetic line. These particles, falling from the solar wind into the Earth's magnetic field, are divided into two parts: one part along the magnetic lines of force immediately flows into the polar regions of the Earth, and the other gets inside the teroid and moves inside it, as can be done according to the left-hand rule, along closed curve ABC. Ultimately, these protons and electrons also flow along geomagnetic lines to the region of the poles, where their increased concentration appears. Protons and electrons produce ionization and excitation of atoms and molecules of gases. They have enough energy for this. Since protons arrive on Earth with energies of 10,000-20,000 eV (1 eV = 1.6 10 J), and electrons with energies of 10-20 eV. But for the ionization of atoms it is necessary: ​​for hydrogen - 13.56 eV, for oxygen - 13.56 eV, for nitrogen - 124.47 eV, and even less for excitation.

Based on the principle that occurs in tubes with rarefied gas when currents are passed through them, excited gas atoms give back the received energy in the form of light.

The green and red glow, according to the results of a spectral study, belongs to excited oxygen atoms, and the infrared and violet glow belongs to ionized nitrogen molecules. Some oxygen and nitrogen emission lines form at an altitude of 110 km, and the red glow of oxygen occurs at an altitude of 200-400 km. The next weak source of red light is hydrogen atoms, formed in the upper layers of the atmosphere from protons arriving from the Sun. Such a proton, after capturing an electron, turns into an excited hydrogen atom and emits red light.

After solar flares, auroral flares usually occur within a day or two. This indicates a connection between these phenomena. Research using rockets has shown that in places of greater intensity of auroras, a higher level of ionization of gases by electrons remains. According to scientists, the maximum intensity of auroras is achieved off the coast of oceans and seas.

There are a number of difficulties for the scientific explanation of all phenomena associated with auroras. That is, the mechanism for accelerating particles to certain energies is not completely known, their trajectories of motion in near-Earth space are not clear, the mechanism for the formation of various types of luminescence is not entirely clear, the origin of sounds is unclear, and not everything agrees quantitatively in the energy balance of ionization and excitation of particles.

Literature used:

1. “Physics in Nature”, author - L. V. Tarasov, Prosveshchenie Publishing House, Moscow, 1988.
2. “Optical phenomena in nature”, author - V. L. Bulat, publishing house “Prosveshchenie”, Moscow, 1974.
3. “Conversations on Physics, Part II”, author - M.I. Bludov, Prosveshchenie Publishing House, Moscow, 1985.
4. “Physics 10”, authors - G. Ya. Myakishev B. B. Bukhovtsev, Prosveshchenie publishing house, Moscow, 1987.
5. “Encyclopedic Dictionary of a Young Physicist”, compiled by V. A. Chuyanov, Pedagogika Publishing House, Moscow, 1984.
6. “Schoolchildren's Handbook on Physics”, compiled by, philological society “Slovo”, Moscow, 1995.
7. “Physics 11”, N. M. Shakhmaev, S. N. Shakhmaev, D. Sh. Shodiev, Prosveshchenie publishing house, Moscow, 1991.
8. “Solving problems in physics”, V. A. Shevtsov, Nizhne-Volzhskoe book publishing house, Volgograd, 1999.

Since ancient times, people have been collecting information about the world in which they live. There was only one science that united all the information about nature that humanity had accumulated at that time. At that time, people did not yet know that they were observing examples of physical phenomena. Currently, this science is called “natural science”.

What does physical science study?

Over time, scientific ideas about the world around us have changed noticeably - there are many more of them. Natural science split into many separate sciences, including: biology, chemistry, astronomy, geography and others. In a number of these sciences, physics occupies not the last place. Discoveries and achievements in this field have allowed humanity to acquire new knowledge. These include the structure and behavior of various objects of all sizes (from giant stars to the smallest particles - atoms and molecules).

The physical body is...

There is a special term “matter”, which in scientific circles is used to describe everything that is around us. A physical body consisting of matter is any substance that occupies a certain place in space. Any physical body in action can be called an example of a physical phenomenon. Based on this definition, we can say that any object is a physical body. Examples of physical bodies: button, notepad, chandelier, cornice, Moon, boy, clouds.

What is a physical phenomenon

Any matter is in constant change. Some bodies move, others come into contact with others, and others rotate. It is not for nothing that many years ago the philosopher Heraclitus uttered the phrase “Everything flows, everything changes.” Scientists even have a special term for such changes - these are all phenomena.

Physical phenomena include everything that moves.

What types of physical phenomena are there?

• Thermal.

These are phenomena when, due to the effects of temperature, some bodies begin to transform (shape, size and condition change). An example of physical phenomena: under the influence of the warm spring sun, icicles melt and turn into liquid; with the onset of cold weather, puddles freeze, boiling water becomes steam.

• Mechanical.

These phenomena characterize a change in the position of one body in relation to the others. Examples: a clock is running, a ball is jumping, a tree is shaking, a pen is writing, water is flowing. They are all in motion.

• Electrical.

The nature of these phenomena fully justifies their name. The word “electricity” has its roots in Greek, where “electron” means “amber.” The example is quite simple and probably familiar to many. When you suddenly take off a woolen sweater, you hear a small crack. If you do this by turning off the light in the room, you can see sparkles.

• Light.

A body participating in a phenomenon associated with light is called luminous. As an example of physical phenomena, we can cite the well-known star of our solar system - the Sun, as well as any other star, a lamp, and even a firefly bug.

• Sound.

The propagation of sound, the behavior of sound waves when colliding with an obstacle, as well as other phenomena that are somehow related to sound, belong to this type of physical phenomena.

• Optical.

They happen thanks to light. For example, humans and animals are able to see because there is light. This group also includes the phenomena of propagation and refraction of light, its reflection from objects and passage through different media.

Now you know what they are physical phenomena. However, it is worth understanding that there is a certain difference between natural and physical phenomena. Thus, during a natural phenomenon, several physical phenomena occur simultaneously. For example, when lightning strikes the ground, the following effects occur: sound, electrical, thermal and light.

About the world around us. In addition to ordinary curiosity, this was caused by practical needs. After all, for example, if you know how to lift
and move heavy stones, you will be able to build strong walls and build a house in which it is more convenient to live than in a cave or dugout. And if you learn to smelt metals from ores and make plows, scythes, axes, weapons, etc., you will be able to plow the field better and get a higher harvest, and in case of danger you will be able to protect your land.

In ancient times, there was only one science - it united all the knowledge about nature that humanity had accumulated by that time. Nowadays this science is called natural science.

Learning about physical science

Another example of an electromagnetic field is light. You will become familiar with some of the properties of light in Section 3.

3. Remembering physical phenomena

The matter around us is constantly changing. Some bodies move relative to each other, some of them collide and, possibly, collapse, others are formed from some bodies... The list of such changes can be continued and continued - it is not without reason that in ancient times the philosopher Heraclitus remarked: “Everything flows, everything changes.” Scientists call changes in the world around us, that is, in nature, a special term - phenomena.

Rice. 1.5. Examples of natural phenomena

Rice. 1.6. Complex natural phenomenon- a thunderstorm can be represented as a combination of a number of physical phenomena

Sunrise and sunset, a snow avalanche, a volcanic eruption, a horse running, a panther jumping - all these are examples of natural phenomena (Fig. 1.5).

To better understand complex natural phenomena, scientists divide them into a collection of physical phenomena - phenomena that can be described using physical laws.

In Fig. Figure 1.6 shows a set of physical phenomena that form a complex natural phenomenon - a thunderstorm. Thus, lightning - a huge electrical discharge - is an electromagnetic phenomenon. If lightning strikes a tree, it will flare up and begin to release heat - physicists in this case talk about a thermal phenomenon. The rumble of thunder and the crackle of flaming wood are sound phenomena.

Examples of some physical phenomena are given in the table. Take a look at the first row of the table, for example. What can be common between the flight of a rocket, the fall of a stone and the rotation of an entire planet? The answer is simple. All examples of phenomena given in this line are described by the same laws - the laws of mechanical motion. Using these laws, we can calculate the coordinates of any moving body (be it a stone, a rocket or a planet) at any point in time that interests us.

Rice. 1.7 Examples of electromagnetic phenomena

Each of you, taking off a sweater or combing your hair with a plastic comb, probably paid attention to the tiny sparks that appeared. Both these sparks and the mighty discharge of lightning belong to the same electromagnetic phenomena and, accordingly, are subject to the same laws. Therefore, you should not wait for a thunderstorm to study electromagnetic phenomena. It is enough to study how safe sparks behave in order to understand what to expect from lightning and how to avoid possible danger. For the first time such research was carried out by the American scientist B. Franklin (1706-1790), who invented an effective means of protection against lightning discharges - a lightning rod.

Having studied physical phenomena separately, scientists establish their relationship. Thus, a lightning discharge (an electromagnetic phenomenon) is necessarily accompanied by a significant increase in temperature in the lightning channel (a thermal phenomenon). The study of these phenomena in their interrelation made it possible not only to better understand the natural phenomenon of a thunderstorm, but also to find a way for the practical application of electromagnetic and thermal phenomena. Surely each of you, passing by a construction site, saw workers in protective masks and blinding flashes of electric welding. Electric welding (a method of joining metal parts using an electric discharge) is an example of the practical use of scientific research.

4. Determine what physics studies

Now that you have learned what matter and physical phenomena are, it is time to determine what the subject of physics is. This science studies: the structure and properties of matter; physical phenomena and their relationships.

• let's sum it up

The world around us consists of matter. There are two types of matter: the substance from which all physical bodies are made, and the field.

Changes are constantly taking place in the world that surrounds us. These changes are called phenomena. Thermal, light, mechanical, sound, electromagnetic phenomena are all examples of physical phenomena.

The subject of physics is the structure and properties of matter, physical phenomena and their relationships.

• Security questions

What does physics study? Give examples of physical phenomena. Can events that occur in a dream or imagination be considered physical phenomena? 4. What substances do the following bodies consist of: a textbook, a pencil, a soccer ball, a glass, a car? What physical bodies can consist of glass, metal, wood, plastic?

Physics. 7th grade: Textbook / F. Ya. Bozhinova, N. M. Kiryukhin, E. A. Kiryukhina. - X.: Publishing house "Ranok", 2007. - 192 p.: ill.

Physical bodies are " actors» physical phenomena. Let's get to know some of them.

Mechanical phenomena

Mechanical phenomena are the movement of bodies (Fig. 1.3) and their action on each other, for example repulsion or attraction. The action of bodies on each other is called interaction.

We will get to know mechanical phenomena in more detail this academic year.

Rice. 1.3. Examples of mechanical phenomena: movement and interaction of bodies during sports competitions (a, b. c); movement of the Earth around the Sun and its rotation around its own axis (r)

Sound phenomena

Sound phenomena, as the name suggests, are phenomena involving sound. These include, for example, the propagation of sound in air or water, as well as the reflection of sound from various obstacles - say, mountains or buildings. When sound is reflected, a familiar echo appears.

Thermal phenomena

Thermal phenomena are the heating and cooling of bodies, as well as, for example, evaporation (the transformation of a liquid into steam) and melting (the transformation of a solid into a liquid).

Thermal phenomena are extremely widespread: for example, they determine the water cycle in nature (Fig. 1.4).

Rice. 1.4. Water cycle in nature

The water of the oceans and seas, heated by the sun's rays, evaporates. As the steam rises, it cools, turning into water droplets or ice crystals. They form clouds from which water returns to Earth in the form of rain or snow.

The real “laboratory” of thermal phenomena is the kitchen: whether soup is being cooked on the stove, whether water is boiling in a kettle, whether food is frozen in the refrigerator - all these are examples of thermal phenomena.

The operation of a car engine is also determined by thermal phenomena: when gasoline burns, a very hot gas is formed, which pushes the piston (motor part). And the movement of the piston is transmitted through special mechanisms to the wheels of the car.

Electrical and magnetic phenomena

The most striking (in the literal sense of the word) example of an electrical phenomenon is lightning (Fig. 1.5, a). Electric lighting and electric transport (Fig. 1.5, b) became possible thanks to the use of electrical phenomena. Examples of magnetic phenomena are the attraction of iron and steel objects by permanent magnets, as well as the interaction of permanent magnets.

Rice. 1.5. Electrical and magnetic phenomena and their uses

The compass needle (Fig. 1.5, c) rotates so that its “north” end points north precisely because the needle is a small permanent magnet, and the Earth is a huge magnet. The Northern Lights (Fig. 1.5, d) are caused by the fact that electrically charged particles flying from space interact with the Earth as with a magnet. Electrical and magnetic phenomena determine the operation of televisions and computers (Fig. 1.5, e, f).

Optical phenomena

Wherever we look, we will see optical phenomena everywhere (Fig. 1.6). These are phenomena associated with light.

An example of an optical phenomenon is the reflection of light by various objects. Rays of light reflected by objects enter our eyes, thanks to which we see these objects.

Rice. 1.6. Examples of optical phenomena: The sun emits light (a); The moon reflects sunlight (b); Mirrors (c) reflect light especially well; one of the most beautiful optical phenomena - rainbow (d)