Optical experiments. Optical illusion. Optical illusions. Home experiment in physics with inertia

Broken pencil

Experiment with arrows

This will surprise not only children, but also adults!

You can still conduct a couple of Piaget experiments with children. For example, take the same amount of water and pour it into different glasses (for example, wide and short, and the second - narrow and tall.) And then ask which one has more water?
You can also put the same number of coins (or buttons) in two rows (one below the other). Ask if the quantity in two rows is the same. Then, removing one coin from one row, move the rest apart so that this row is the same in length as the top one. And again ask if it’s the same now, etc. Try it – the answers will probably surprise you!

Ebbinghaus illusion or Titchener circles- optical illusion of perception of relative sizes. The most famous version of this illusion is that two circles, identical in size, are placed side by side, with large circles around one of them, while the other is surrounded by small circles; in this case, the first circle seems smaller than the second.

The two orange circles are exactly the same size; however, the left circle appears smaller

Müller-Lyer illusion

The illusion is that the segment framed by the “points” appears shorter than the segment framed by the “tail” arrows. The illusion was first described by German psychiatrist Franz Müller-Lyer in 1889

Or, for example, an optical illusion - first you see black, then white

Even more optical illusions

And finally, the illusion toy is Thaumatrope.

When you quickly rotate a small piece of paper with two designs on different sides, they are perceived as one. You can make such a toy yourself by drawing or gluing the corresponding images (several common thaumatropes - flowers and a vase, a bird and a cage, a beetle and a jar) on fairly thick paper and attach strings to the sides for twisting. Or even easier - attach it to a stick, like a lollipop, and quickly rotate it between your palms.

And a couple more pictures. What do you see on them?

By the way, in our store you can buy ready-made kits for conducting experiments in the field of optical illusions!

Introduction

1.Literature review

1.1. History of the development of geometric optics

1.2. Basic concepts and laws geometric optics

1.3. Prism elements and optical materials

2. Experimental part

2.1. Materials and experimental methods

2.2. Experimental results

2.2.1. Demonstration experiments using a glass prism with a refractive angle of 90º

2.2.2. Demonstration experiments using a glass prism filled with water, with a refractive angle of 90º

2.2.3. Demonstration experiments using a hollow glass prism, filled with air, with a refractive angle of 74º

2.3. Discussion of experimental results

List of used literature

Introduction

The decisive role of experiment in the study of physics at school corresponds to the main principle of the natural sciences, according to which experiment is the basis for the knowledge of phenomena. Demonstration experiments contribute to the creation physical concepts. Among demonstration experiments, one of the most important places is occupied by experiments in geometric optics, which make it possible to clearly show the physical nature of light and demonstrate the basic laws of light propagation.

In this work, the problem of setting up experiments in geometric optics using a prism in high school. The most visual and interesting experiments in optics were selected using equipment that can be purchased by any school or made independently.

Literature review

1.1 History of the development of geometric optics.

Optics is one of those sciences, the initial ideas of which arose in ancient times. Throughout its centuries-old history, it has experienced continuous development, and is currently one of the fundamental physical sciences, enriched by the discoveries of ever new phenomena and laws.

The most important problem in optics is the question of the nature of light. The first ideas about the nature of light arose in ancient times. Ancient thinkers tried to understand the essence of light phenomena based on visual sensations. The ancient Hindus thought that the eye was of a “fiery nature.” The Greek philosopher and mathematician Pythagoras (582-500 BC) and his school believed that visual sensations arise due to the fact that “hot vapors” emanate from the eyes to objects. In their further development, these views took a clearer form in the form of the theory of visual rays, which was developed by Euclid (300 BC). According to this theory, vision is due to the fact that “visual rays” flow from the eyes, which touch the body with their ends and create visual sensations. Euclid is the founder of the doctrine of the rectilinear propagation of light. Applying mathematics to the study of light, he established the laws of reflection of light from mirrors. It should be noted that for the construction of a geometric theory of light reflection from mirrors, the nature of the origin of light does not matter, but only the property of its rectilinear propagation is important. The patterns discovered by Euclid have been preserved in modern geometric optics. Euclid was also familiar with the refraction of light. At a later time, similar views were developed by Ptolemy (70-147 AD). They paid great attention to the study of the phenomena of light refraction; in particular, Ptolemy made many measurements of the angles of incidence and refraction, but he was unable to establish the law of refraction. Ptolemy noticed that the position of the luminaries in the sky changes due to the refraction of light in the atmosphere.

In addition to Euclid, other ancient scientists also knew the effect of concave mirrors. Archimedes (287-212 BC) is credited with burning the enemy fleet with the help of a system of concave mirrors, with which he collected the sun's rays and directed them at Roman ships. A certain step forward was made by Empedocles (492-432 BC), who believed that outflows were directed from luminous bodies to the eyes, and outflows emanated from the eyes towards the bodies. When these outflows meet, visual sensations arise. The famous Greek philosopher, founder of atomism, Democritus (460-370 BC) completely rejects the idea of ​​visual rays. According to the views of Democritus, vision is caused by the fall of small atoms emanating from objects onto the surface of the eye. Similar views were later held by Epicurus (341-270 BC). A decisive opponent of the “theory of visual rays” was the famous Greek philosopher Aristotle (384-322 BC), who believed that the cause of visual sensations lies outside the human eye. Aristotle attempted to explain colors as a consequence of the mixing of light and darkness.

It should be noted that the views of ancient thinkers were mainly based on simple observations of natural phenomena. Ancient physics did not have the necessary foundation in the form of experimental research. Therefore, the teaching of the ancients about the nature of light is speculative. Nevertheless, although these views are mostly just brilliant guesses, they certainly had a great influence on the further development of optics.

The Arab physicist Alhazen (1038) developed a number of issues in optics in his research. He studied the eye, the refraction of light, the reflection of light in concave mirrors. When studying the refraction of light, Algazei, in contrast to Ptolemy, proved that the angles of incidence and refraction are not proportional, which was the impetus for further research in order to find the law of refraction. Alhazen is familiar with the magnifying power of spherical glass segments. On the question of the nature of light, Alhazen takes the right position, rejecting the theory of visual rays. Algazen proceeds from the idea that rays emanate from each point of a luminous object, which, reaching the eye, cause visual sensations. Alhazen believed that light had a finite speed of propagation, which in itself represented a major step in understanding the nature of light. Alhazen gave the correct explanation for the fact that the Sun and Moon appear larger at the horizon than at the zenith; he explained this as a deception of feelings.

Renaissance. In the field of science, the experimental method of studying nature is gradually winning. During this period, a number of outstanding inventions and discoveries were made in optics. Francis Maurolicus (1494 -1575) is credited with providing a fairly accurate explanation of the action of glasses. Mavrolik also found that concave lenses do not collect, but scatter rays. He established that the lens is the most important part of the eye, and made a conclusion about the causes of farsightedness and myopia as consequences of abnormal refraction of light by the lens. Mavrolik gave the correct explanation for the formation of images of the Sun observed when solar rays pass through small holes. Next we should name the Italian Porta (1538-1615), who in 1589 invented the camera obscura - the prototype of the future camera. A few years later, the basic optical instruments were invented - the microscope and the telescope.

The invention of the microscope (1590) is associated with the name of the Dutch master optician Zachary Jansen. Spotting scopes began to be manufactured approximately simultaneously (1608-1610) by the Dutch opticians Zachary Jansen, Jacob Metius and Hans Lippershey. The invention of these optical instruments led in subsequent years to major discoveries in astronomy and biology. The German physicist and astronomer N. Kepler (1571-1630) authored fundamental works on the theory of optical instruments and physiological optics, the founder of which he can rightfully be called. Kepler worked a lot on the study of the refraction of light.

Fermat's principle, named after the French scientist Pierre Fermat (1601-1665), was of great importance for geometric optics. This principle established that light between two points travels along a path that takes a minimum of time to travel. It follows that Fermat, in contrast to Descartes, considered the speed of light to be finite. The famous Italian physicist Galileo (1564-1642) did not conduct systematic work devoted to the study of light phenomena. However, he also carried out work in optics that brought remarkable results to science. Galileo improved the telescope and first applied it to astronomy, in which he made outstanding discoveries that helped substantiate the newest views on the structure of the Universe, based on the heliocentric system of Copernicus. Galileo managed to create a telescope with a magnification of frame 30, which was many times greater than the magnification of the telescopes of its first inventors. With its help, he discovered mountains and craters on the surface of the Moon, discovered satellites near the planet Jupiter, discovered the stellar structure of the Milky Way, etc. Galileo tried to measure the speed of light under terrestrial conditions, but was not successful due to the weakness of the experimental means available for this purpose . It follows that Galileo already had correct ideas about final speed propagation of light. Galileo also observed sunspots. The priority of Galileo's discovery of sunspots was challenged by the Jesuit scientist Pater Scheiner (1575-1650), who made precise observations of sunspots and solar faculae using a telescope designed according to Kepler's design. The remarkable thing about Scheiner’s work is that he turned the telescope into a projection device, extending the eyepiece more than was necessary for clear vision with the eye, this made it possible to obtain an image of the Sun on the screen and demonstrate it at varying degrees of magnification to several people at the same time.

The 17th century is characterized by further progress in various fields of science, technology and production. Mathematics is undergoing significant development. Scientific societies and academies uniting scientists are being created in various European countries. Thanks to this, science becomes available to wider circles, which contributes to the establishment of international connections in science. In the second half of the 17th century, the experimental method of studying natural phenomena finally won.

The largest discoveries of this period are associated with the name of the brilliant English physicist and mathematician Isaac Newton / (1643-1727). Newton's most important experimental discovery in optics was the dispersion of light in a prism (1666). By studying the passage of a beam of white light through a triangular prism, Newton found that a beam of white light splits into an infinite collection of colored rays forming a continuous spectrum. From these experiments it was concluded that white light is a complex radiation. Newton also performed the opposite experiment, using a lens to collect colored rays formed after a beam of white light passed through a prism. As a result, he again received white light. Finally, Newton experimented with mixing colors using a rotating circle divided into several sectors, colored in the primary colors of the spectrum. When the disk rotated quickly, all the colors merged into one, creating the impression of white.

Newton laid the results of these fundamental experiments as the basis for the theory of colors, which none of his predecessors had previously succeeded in achieving. According to color theory, the color of a body is determined by those rays of the spectrum that this body reflects; the body absorbs other rays.

1.2 Basic concepts and laws of geometric optics. The branch of optics, which is based on the idea of ​​light rays as straight lines along which light energy propagates, is called geometric optics. This name was given to it because all phenomena of the propagation of light here can be studied by geometric constructions of the path of rays, taking into account the law of reflection and refraction of light. This law is the basis of geometric optics.

However, where we are talking about phenomena involving the interaction of light with obstacles whose dimensions are quite small, the laws of geometric optics turn out to be insufficient and it is necessary to use the laws of wave optics. Geometric optics makes it possible to analyze the basic phenomena associated with the passage of light through lenses and other optical systems, as well as with the reflection of light from mirrors. The concept of a light beam as an infinitely thin beam of light propagating in a straight line naturally leads to the laws of rectilinear propagation of light and independent propagation of light beams. It is these laws, together with the laws of refraction and reflection of light, that are the basic laws of geometric optics, which not only explain many physical phenomena, but also allow for calculations and design of optical instruments. All these laws were initially established as empirical, that is, based on experiments and observations.

Didactic material

Spread of light

As we know, one type of heat transfer is radiation. With radiation, the transfer of energy from one body to another can occur even in a vacuum. There are several types of radiation, one of them is visible light.

Illuminated bodies gradually heat up. This means that light really is radiation.

Light phenomena are studied by a branch of physics called optics. The word "optics" in Greek means "visible", because light is a visible form of radiation.

The study of light phenomena is extremely important for humans. After all, we receive more than ninety percent of information through vision, that is, the ability to perceive light sensations.

Bodies that emit light are called light sources - natural or artificial.

Examples of natural light sources are the Sun and other stars, lightning, luminous insects and plants. Artificial light sources are a candle, lamp, burner and many others.

In any light source, energy is consumed during radiation.

The sun emits light thanks to energy from nuclear reactions occurring in its depths.

A kerosene lamp converts the energy released when kerosene is burned into light.

Reflection of light

A person sees a light source when a ray emanating from this source enters the eye. If the body is not a source, then the eye can perceive rays from some source reflected by this body, that is, falling on the surface of this body and thereby changing the direction of further propagation. The body that reflects the rays becomes a source of reflected light.

The rays falling on the surface of the body change the direction of further propagation. When reflected, light returns to the same medium from which it fell on the surface of the body. The body that reflects the rays becomes a source of reflected light.

When we hear this word "reflection", first of all, we are reminded of a mirror. Flat mirrors are most often used in everyday life. Using a flat mirror, you can conduct a simple experiment to establish the law by which light is reflected. Let's place the illuminator on a sheet of paper lying on the table so that a thin beam of light lies in the plane of the table. In this case, the light beam will slide over the surface of the sheet of paper, and we will be able to see it.

Let us install a flat mirror vertically in the path of a thin light beam. A beam of light will be reflected from it. You can make sure that the reflected beam, like the beam incident on the mirror, slides along the paper in the plane of the table. Mark with a pencil on a piece of paper relative position both light beams and the mirror. As a result, we obtain a diagram of the experiment. The angle between the incident beam and the perpendicular restored to the reflecting surface at the point of incidence is usually called the angle of incidence in optics. The angle between the same perpendicular and the reflected ray is the angle of reflection. The results of the experiment are as follows:

1. The incident ray, the reflected ray, and the perpendicular to the reflecting surface reconstructed at the point of incidence lie in the same plane.
2. The angle of incidence is equal to the angle of reflection. These two conclusions represent the law of reflection.

Looking at a flat mirror, we see images of objects that are located in front of it. These images exactly repeat appearance items. It seems that these duplicate objects are located behind the surface of the mirror.

Consider the image of a point source in a plane mirror. To do this, we will arbitrarily draw several rays from the source, construct the corresponding reflected rays, and then construct extensions of the reflected rays beyond the plane of the mirror. All continuations of the rays will intersect behind the mirror plane at one point: this point is the image of the source.

Since it is not the rays themselves that converge in the image, but only their continuations, in reality there is no image at this point: it only seems to us that the rays are emanating from this point. Such an image is usually called imaginary.

Refraction of light

When light reaches the interface between two media, part of it is reflected, while the other part passes through the boundary, being refracted, that is, changing the direction of further propagation.

A coin immersed in water appears larger to us than when it just lies on the table. A pencil or spoon placed in a glass of water appears to us to be broken: the part in the water appears raised and slightly enlarged. These and many others optical phenomena explained by the refraction of light.

The refraction of light is due to the fact that different environments light travels at different speeds.

The speed of light propagation in a particular medium characterizes optical density of a given medium: the higher the speed of light in a given medium, the lower its optical density.

How does the angle of refraction change when light passes from air to water and when light passes from water to air? Experiments show that when moving from air to water, the angle of refraction turns out to be smaller than the angle of incidence. And vice versa: when passing from water to air, the angle of refraction turns out to be greater than the angle of incidence.

From experiments on the refraction of light, two facts became obvious: 1. The incident ray, the refracted ray and the perpendicular to the interface between the two media, restored at the point of incidence, lie in the same plane.

1. When moving from an optically denser medium to an optically less dense medium, the angle of refraction is greater than the angle of incidence.When moving from an optically less dense medium to an optically denser one, the angle of refraction is less than the angle of incidence.

An interesting phenomenon can be observed if the angle of incidence is gradually increased as light passes into an optically less dense medium. The angle of refraction in this case, as is known, is greater than the angle of incidence, and, with an increase in the angle of incidence, the angle of refraction will also increase. At a certain value of the angle of incidence, the angle of refraction will become equal to 90°.

We will gradually increase the angle of incidence as light passes into an optically less dense medium. As the angle of incidence increases, the angle of refraction will also increase. When the angle of refraction becomes equal to ninety degrees, the refracted ray does not pass into the second medium from the first, but slides in the plane of the interface between these two media.

This phenomenon is called total internal reflection, and the angle of incidence at which it occurs is called the limiting angle of total internal reflection.

The phenomenon of total internal reflection is widely used in technology. This phenomenon is the basis for the use of flexible optical fibers through which light rays, reflecting repeatedly from the walls.

Light does not leave the fiber due to total internal reflection. A simpler optical device that uses total internal reflection is a reversible prism: it flips the image, reversing the rays entering it.

Lens image

A lens whose thickness is small compared to the radii of the spheres forming the surface of this lens is called thin. In what follows, we will only consider thin lenses. On optical diagrams, thin lenses are depicted as segments with arrows at the ends. Depending on the direction of the arrows, the diagrams distinguish between converging and diverging lenses.

Let's consider how a beam of rays parallel to the main optical axis passes through the lenses. Passing through

converging lens, the rays are concentrated at one point. Having passed through a diverging lens, the rays diverge into different sides in such a way that all their extensions converge at one point lying in front of the lens.

The point at which rays parallel to the main optical axis are collected after refraction in a collecting lens is called the main focus of the lens-F.

In a diverging lens, rays parallel to its main optical axis are scattered. The point at which the continuations of the refracted rays are collected lies in front of the lens and is called the main focus of the diverging lens.

The focus of a diverging lens is obtained at the intersection not of the rays themselves, but of their continuations, therefore it is imaginary, in contrast to a converging lens, which has a real focus.

The lens has two main focuses. They both lie on equal distances from the optical center of the lens on its main optical axis.

The distance from the optical center of the lens to the focus is usually called the focal length of the lens. The more the lens changes the direction of the rays, the shorter its focal length is. Therefore, the optical power of a lens is inversely proportional to its focal length.

Optical power is usually denoted by the letter "DE" and is measured in diopters. For example, when writing a prescription for glasses, they indicate how many diopters the optical power of the right and left lenses should be.

diopter (dopter) is the optical power of a lens whose focal length is 1 m. Since converging lenses have real foci, and diverging lenses have imaginary foci, we agreed to consider the optical power of converging lenses to be a positive value, and the optical power of diverging lenses to be negative.

Who established the law of light reflection?

For the 16th century, optics was an ultra-modern science. From a glass ball filled with water, which was used as a focusing lens, a magnifying glass emerged, and from it a microscope and a telescope. The Netherlands, the largest maritime power at that time, needed good telescopes in order to examine the dangerous coast in advance or to escape from the enemy in time. Optics ensured the success and reliability of navigation. Therefore, it was in the Netherlands that many scientists studied it. The Dutchman Willebrord, Snel van Rooyen, who called himself Snellius (1580 - 1626), observed (as, however, many before him had seen) how a thin ray of light was reflected in a mirror. He simply measured the angle of incidence and the angle of reflection of the beam (which no one had done before) and established the law: the angle of incidence is equal to the angle of reflection.

Source. Mirror world. Gilde V. - M.: Mir, 1982. p. 24.

Why are diamonds so highly valued?

Obviously, a person values ​​especially highly everything that cannot be changed or is difficult to change. Including precious metals and stones. The ancient Greeks called the diamond “adamas” - irresistible, which expressed their special attitude towards this stone. Of course, for uncut stones (diamonds were not cut either) the most obvious properties were hardness and brilliance.

Diamonds have a high refractive index; 2.41 for red and 2.47 for violet (for comparison, suffice it to say that the refractive index of water is 1.33, and glass, depending on the type, is from 1.5 to 1.75).

White light is made up of the colors of the spectrum. And when its ray is refracted, each of the component colored rays is deflected differently, as if it were split into the colors of the rainbow. This is why there is a “play of colors” in a diamond.

The ancient Greeks undoubtedly admired this too. Not only is the stone exceptional in brilliance and hardness, it is also shaped like one of Plato's "perfect" solids!

Experiments

Optics EXPERIENCE #1

Explain the darkening of a block of wood after it is wetted.

Equipment: vessel with water, wooden block.

Explain the vibration of the shadow of a stationary object when light passes through the air above a burning candle. Equipment: tripod, ball on a string, candle, screen, projector.

Glue colored pieces of paper onto the fan blades and observe how the colors add up under different rotation modes. Explain the observed phenomenon.

EXPERIENCE No. 2

By interference of light.

Simple demonstration of light absorption aqueous solution dye

For its preparation it requires only a school illuminator, a glass of water and a white screen. Dyes can be very diverse, including fluorescent.

Students observe with great interest the color change of a beam of white light as it propagates through the dye. What is unexpected for them is the color of the beam emerging from the solution. Since the light is focused by the illuminator lens, the color of the spot on the screen is determined by the distance between the glass of liquid and the screen.

Simple experiments with lenses. (EXPERIMENT No. 3)

What happens to the image of an object obtained using a lens if part of the lens breaks and the image is obtained using the remaining part?

Answer . The image will be obtained in the same place where it was obtained using the whole lens, but its illumination will be less, because a minority of the rays leaving the object will reach its image.

Place a small shiny object, for example, a ball from a bearing, or a bolt from a computer, on a table illuminated by the Sun (or a powerful lamp) and look at it through a tiny hole in a piece of foil. Multi-colored rings or ovals will be clearly visible. What kind of phenomenon will be observed? Answer. Diffraction.

Simple experiments with colored glasses. (EXPERIMENT No. 4)

On a white sheet of paper, write “excellent” with a red felt-tip pen or pencil and “good” with a green felt-tip pen. Take two bottle glass fragments - green and red.

(Warning! Be careful, you can get hurt on the edges of the fragments!)

What kind of glass do you have to look through to see an “excellent” rating?

Answer . You must look through green glass. In this case, the inscription will be visible in black on the green background of the paper, since the red light of the inscription “excellent” is not transmitted by the green glass. When viewed through red glass, the red inscription will not be visible on the red background of the paper.

EXPERIMENT No. 5: Observation of the dispersion phenomenon

It is known that when a narrow beam of white light is passed through a glass prism, a rainbow stripe called the dispersive (or prismatic) spectrum can be observed on a screen installed behind the prism. This spectrum is also observed when the light source, prism and screen are placed in a closed vessel from which the air has been evacuated.

The results of the latest experiment show that there is a dependence of the absolute refractive index of glass on the frequency of light waves. This phenomenon is observed in many substances and is called light dispersion. There are various experiments to illustrate the phenomenon of light dispersion. The figure shows one of the options for carrying it out.

The phenomenon of light dispersion was discovered by Newton and is considered one of his most important discoveries. The tombstone, erected in 1731, depicts figures of young men holding in their hands the emblems of the most important discoveries Newton. In the hands of one of the young men is a prism, and in the inscription on the monument there are the following words: “He investigated the difference in light rays and the various properties of colors that appeared at the same time, which no one had previously suspected.”

EXPERIENCE #6: Does the mirror have a memory?

How to place a flat mirror on a drawn rectangle to get an image: a triangle, a quadrangle, a pentagon. Equipment: a flat mirror, a sheet of paper with a square drawn on it.

QUESTIONS

Transparent plexiglass becomes matte if its surface is rubbed with sandpaper. The same glass becomes transparent again if you rub it....How?

The numbers on the lens aperture scale are equal to the ratio focal length to hole diameter: 2; 2.8; 4.5; 5; 5.8, etc. How will the shutter speed change if the aperture is moved to a larger scale division?

Answer. How larger number the aperture indicated on the scale, the lower the illumination of the image, and the longer the shutter speed required when photographing.

Most often, camera lenses consist of several lenses. Light passing through the lens is partially reflected from the surfaces of the lenses. What defects does this lead to when shooting?Answer

When shooting snowy plains and water surfaces on sunny days, it is recommended to use a solar hood, which is a cylindrical or conical tube blackened inside and placed on the
lens. What is the purpose of the hood?Answer

To prevent light from being reflected inside the lens, a thin transparent film of the order of ten-thousandths of a millimeter is applied to the surface of the lenses. Such lenses are called coated lenses. On which physical phenomenon Is it based on lens coating? Explain why lenses do not reflect light.Answer.

Question for forum

Why does black velvet appear so much darker than black silk?

Why does white light, passing through a window glass, not decompose into its components?Answer.

Blitz

1. What are glasses without arms called? (Pince-nez)

2. What gives away an eagle during a hunt? (Shadow.)

3. What is the artist Kuinzhi famous for? (The ability to depict the transparency of air and moonlight)

4. What are the lamps that illuminate the stage called? (Soffits)

5. Is the gemstone blue or greenish in color?(Turquoise)

6. Indicate at what point the fish is in the water if the fisherman sees it at point A.

Blitz

1. What can't you hide in a chest? (Beam of light)

2. What color is white light? (White light consists of a number of multi-colored rays: red, orange, yellow, green, blue, indigo, violet)

3. What's bigger: the cloud or its shadow? (The cloud casts a cone of full shadow tapering towards the ground, the height of which is large due to the significant size of the cloud. Therefore, the shadow of the cloud differs little in size from the cloud itself)

4. You are behind her, she is from you, you are from her, she is behind you. What is it? (Shadow)

5. You can see the edge, but you can’t reach it. What is this? (horizon)

Optical illusions.

Don't you think the black and white stripes are moving in opposite directions? If you tilt your head - now to the right, now to the left - the direction of rotation also changes.

An endless staircase leading up.

Sun and eye

Don't be like the sun's eyes,

He wouldn't be able to see the Sun... W. Goethe

The comparison between the eye and the Sun is as old as the human race itself. The source of this comparison is not science. And in our time, next to science, simultaneously with the picture of phenomena revealed and explained by the new natural science, the world of ideas of a child and primitive man and, intentionally or unintentionally, the world of poets imitating them. It is sometimes worth looking into this world as one of the possible sources scientific hypotheses. He is amazing and fabulous; in this world, bridges-connections are boldly thrown between natural phenomena, which sometimes science is not yet aware of. IN in some cases these connections are guessed correctly, sometimes they are fundamentally erroneous and simply absurd, but they always deserve attention, since these errors often help to understand the truth. Therefore, it is instructive to approach the question of the connection between the eye and the Sun first from the point of view of children's, primitive and poetic ideas.

When playing “hide and seek”, a child very often decides to hide in the most unexpected way: he closes his eyes or covers them with his hands, being sure that now no one will see him; for him vision is identified with light.

Even more surprising, however, is the preservation of the same instinctive mixture of vision and light in adults. Photographers, that is, people somewhat experienced in practical optics, often catch themselves closing their eyes when, when loading or developing plates, they need to carefully monitor that light does not penetrate into a dark room.

If you listen carefully to how we speak, to our own words, then traces of the same fantastic optics are immediately revealed here.

Without noticing this, people say: “the eyes sparkled,” “the sun came out,” “the stars are looking.”

For poets, transferring visual ideas to the luminary and, conversely, attributing to the eyes the properties of light sources is the most common, one might say, obligatory technique:

Stars of the night

Like accusing eyes

They look at him mockingly.

His eyes are shining.

A.S. Pushkin.

We looked at the stars with you,

They're on us. Fet.

How does the fish see you?

Due to the refraction of light, the fisherman sees the fish not where it actually is.

Folk signs

How to place a flat mirror on a drawn rectangle to get an image: a triangle, a quadrangle, a pentagon. Equipment: a flat mirror, a sheet of paper with a square drawn on it. Answer

FILM FRAGMENT

Watson, I have a small task for you,” Sherlock Holmes said, shaking his friend’s hand. - Remember the murder of the jeweler, the police claim that the driver of the car was driving at a very low speed, and the jeweler himself threw himself under the wheels of the car, so the driver did not have time to brake. But it seems to me that everything was wrong, the car was driving at high speed and murder Intentionally. It is difficult to determine the truth now, but I learned that this episode was accidentally caught on film, since the film was being filmed at that time. So I ask you, Watson, get this episode, literally a few meters of film.

But what will this give you? - asked Watson.

I don’t know yet, was the answer.

After some time, the friends sat in the cinema hall and, at the request of Sherlock Holmes, watched a small episode.

The car had already driven some distance, the jeweler was lying on the road almost motionless. A cyclist on a sports racing bike passes near the lying jeweler.

Notice, Watson, that a cyclist has the same speed as a car. The distance between the cyclist and the car does not change throughout the entire episode.

And what follows from this? - Watson was perplexed.

Just a minute, let’s look at the episode again,” Holmes whispered calmly.

The episode was repeated. Sherlock Holmes was thoughtful.

Watson, did you notice the cyclist? - the detective asked again.

Yes, their speeds were the same,” confirmed Dr. Watson.

Have you noticed the cyclist's wheels? - Holmes asked.

The wheels, like wheels, consist of three spokes located at an angle of 120°, “an ordinary racing bicycle,” the doctor reasoned.

But how did you count the number of spokes? – asked the famous detective.

Very simply, while watching the episode, I got the impression that... the cyclist is standing still, since the wheels do not rotate.

But the cyclist was moving,” Sherlock Holmes clarified.

It moved, but the wheels did not rotate,” Watson confirmed.