Amazing optical illusions: how they work. It turns out that scientists are also dealing with this issue, and they say that there are many scientific areas that are trying to understand how we perceive the world around us.

Optical illusions exploit the difference between what your eyes see and what your brain perceives. They demonstrate how your visual system edits an image before you even know it, just like your personal assistant sifting the important from the unimportant. People have been creating optical illusions long before they knew how they work. To date, advances in neuroscience have made it possible to understand how visual processes work that deceive your brain. But there are also those that have not yet been explained.

Illusion with a shadow on a chessboard

Everyone knows the illusion where a shadow falls from the body onto the chessboard, and two cells located outside the shadow and within it look different, black and white. But in fact they are the same color. Edward Adelson in 1995 used this illusion to show people how the human visual system perceives a shadow. When trying to determine the color of a surface, the brain takes into account that the surface is in shadow and automatically signals that it should be rendered as lighter. Thus, the brain interprets the cell in the shadow as lighter, but in fact it has the same color as the cell outside the shadow.

Lilac Chase

This optical illusion is a black crosshair in the center of a circle of purple spots. In turn, these spots disappear, merging with the gray background. Your task is to focus on the crosshairs and wait - you will notice that the purple spots do not actually disappear, but become green! This visual trick is called the Troxler effect and was discovered in 1804. This effect communicates that the human eye is able to focus on something moving, active, ignoring everything else. Your eyes take a little time to adjust when you're focusing on the crosshairs to get used to, and then they start to follow the changing dot, which turns out to be green and the purples fade into the background as unimportant.

fading light

If you focus on the blinking light in the center, you will notice that the yellow dots scattered around the light source begin to randomly disappear and appear in unexpected places. This is due to a phenomenon called motion-induced blindness. It does not yet have a generally accepted explanation, but most scientists believe that it originates in the primary visual cortex, the part of the brain that is responsible for processing information about static and dynamic objects.

Goering's illusion

In this geometric optical illusion, the stripes look like they are curved outwards. Hering attributes this effect to the fact that the human brain overestimates the angle of intersection of the red vertical and the rest of the blue stripes. But why is this miscalculation happening? Most likely, this is due to the human tendency to visually predict the future. Light hits the retina extremely quickly, so the human visual system has gradually evolved to compensate for the delay between light hitting the retina and delivering the signal to the brain.

Illusion of gradation

The horizontal stripe in this optical illusion changes its color from light to dark, being on exactly the same, but only the opposite background, which changes from dark to light. As you might have guessed, this is just an optical illusion. If you close the background, you will see that the horizontal stripe is the same color. This illusion is similar to the very first one, with a checkerboard - the brain analyzes the environment in which the different parts of the horizontal strip are located, and darkens it where the background is light, and brightens it where the background is dark.

illusory movement

At the moment, there is no clear explanation of what causes the illusory movement. Some believe this is due to small, involuntary eye movements that make you think the image is moving. Others believe that when you look at such a complex pattern, your visual cortex gradually confuses static objects with dynamic ones, so you seem to see movement. In any case, this illusion is also an optical illusion that works under any conditions, and you will not be able to convince your brain.

City scientific and practical conference

schoolchildren and young students

Scientific society of students "Discovery"

MOU "Lyceum №1656"

Direction: PHYSICS

optical illusions

Completed by: Gritsai Dmitry,

Kolesov Dmitry

Grade 9 MOU "Lyceum No. 166"

Supervisor:

Puzhuls Irina Nikolaevna,

higher physics teacher

MOU "Lyceum No. 1656"

Tomsk - 2007

Introduction ...........................................................................................................3

Chapter I . Explanation of optical illusions in terms of

physics, biology, psychology.

1.1. The visual process from the point of view of biology .............................................. 5

1.2. Psychology of vision .................................................................. ....................................5

1.3. Physical assessment of the environment .................................................................. ............6

Chapter II

2.1. Imagination and reality .............................................................. .......................7

2.2. Impossible figures - a feature of the imagination ....................................... 8

Chapter III . Optical illusions.

3.1. Optical illusions are an integral part of human life… 11

3.2. History of discoveries ……………………………………………………..12

3.3. Classification of optical illusions ……………………………..12-15

3.3.1. Illusion of intersection ………………………………………………..12

3.3.2. Illusion of “continuation-break” …………………………………..13

3.3.3. The illusion of curvature ………………………………………………….13

3.3.4. Irradiation ………………………………...………………………...14

3.3.5. External pressure on the dimensions of the object ………………………......15

Conclusion …………………………………………………………………16

Scientific literature ………………………………………………………17

Introduction.

At present, despite the development of science and technology, a person continues to use his subjective assessments in all areas. Of course, if this concerns non-mathematical sciences, then there is nothing wrong with that, but when it comes to estimates, in case of an error in which irreparable things can happen, then one should forget about intuition and use measuring instruments. This, of course, applies to the so-called "by eye" assessment.

The term "illusion" is very common. Unfortunately, our eye is not an accurate instrument in the world, and therefore it tends to make mistakes. These errors are called optical illusions. A very large number of them are known and they are not all of the same type, as well as the reasons for their occurrence. Here are two real life cases:

There is a mountain in California that local motorists say is magnetic. The fact is that on a small section of the road 60 m long at the foot of this mountain, unusual phenomena are observed. This section is sloped. If the engine of a car driving downhill is turned off, then the car rolls backwards, i.e. up the slope, as if obeying the "magnetic attraction" of the mountain. This amazing property of the mountain was considered to be established so reliably that even a board with a description of the phenomenon flaunts in the corresponding place on the road.

There were, however, people who thought it doubtful that the mountain could attract cars. For verification, this section of the road was leveled. The result was unexpected: what everyone thought was a climb turned out to be a 2-degree descent. Such a slope can cause the car to roll without a motor on a very good highway.

The illusion of sight also explains the stories of travelers about rivers in which water flows up the slope. I quote an extract about this from the book of one physiologist, Professor Bernstein, “External Senses”: “In many cases we tend to make mistakes in judging whether a given direction is horizontal, whether it is inclined upwards or downwards. Walking, for example, along a slightly sloping road and seeing at some distance another road meeting the first, we imagine the rise of the second road to be steeper than it really is. We are then surprised to see that the second road is not at all as steep as we expected.

This is explained by the fact that we take the road along which we are going for the main plane, to which we attribute the slope of other directions. We unconsciously identify it with the horizontal plane, and then, naturally, we imagine the slope of the other path to be exaggerated.

This is facilitated by the fact that our muscular feeling does not at all catch slopes of 2-3 degrees when walking. On the streets of Moscow, Kyiv and other hilly cities one often has to observe the illusion about which the physiologist speaks. Even more curious is another optical illusion that happens to be succumbed in uneven terrain: the stream seems to us to be flowing uphill!

When descending along a slightly sloping road along a stream, which has an even smaller fall, i.e. flows almost horizontally, it seems to us that the stream flows up the slope. In this case, we also consider the direction of the road to be horizontal, since we are used to taking the plane on which we stand as the basis for judging the inclination of other planes.

Therefore, in order for people to make fewer mistakes, unconditionally trusting their eyes, they need to take into account some features of their visual apparatus.

Goals of the work:

1. Explain the nature of the occurrence of optical illusions.

2. Explain from the point of view of biology, psychology and physics the possibility of their appearance.

3. Classify optical illusions.

4. Show the application of the features of our imagination on the example of impossible figures.

Tasks:

1. Study literature.

2. Master the methodology of analysis and synthesis.

3. Highlight the essential features of the considered illusions.

4. Group illusions with the same essential features.

5. Draw conclusions.

Scientific novelty:

A classification of optical illusions was carried out.

Chapter I . Explanation of optical illusions

from the point of view of physics, biology, psychology.

1.1. Visual process from the point of view of biology.

The human eye is the most complex optical device with which a person perceives 90% of the life around us. Astronomer and physicist Johannes Kepler in the 19th century considered the device of the eye from the point of view of optics. He showed that an image of surrounding objects is formed on the fundus. According to the laws of optics, such an image should be inverted. That is why a newborn baby sees the world upside down. But gradually the brain begins to flip the image and gets used to it. It is interesting that if a person continues to wear glasses that turn the image over for a long time, then the brain will again put him “on his feet”. But people have not created a lens similar to the lens of the eye to this day. After all, it can, becoming, either more convex, or less “sharp” on near and far objects. But, if this mechanism is violated, then a person develops either farsightedness or myopia, so in this case he has to wear glasses.

The bottom, on which the image falls and is formed in a reduced form, transmits the image to the retina, which perceives it. Between the lens and the retina lies a transparent vitreous body, similar to jelly. Due to the fact that inside the retina there is a visual purple that fades under the influence of light, we can perceive it. The retina is made up of cells called rods and cones. Thanks to the chopsticks, we perceive a black and white image. Cones distinguish color: some are blue, others are green, and still others are red. All other colors are mixed to the human eye.

1.2. Psychology of vision.

At the same time, it is known that the image, having hit our eye and reaching the retina through special brain channels, enters the brain, where it is formed. At the same time, the impulses of the visual system are no different from the impulses of the nerve cells of the nose, the skin of the ear. The brain perceives their messages as visual images only because it knows where they came from. There the person presents the image. But why is the brain capable of presenting an image. Psychology has been dealing with this issue for some time now.

The human brain, in addition to perception, thinking, memory and a number of other mental processes, has a special form of the psyche that is unique to people - imagination.

In nothing else but imagination is the ideal and mysterious character of the psyche manifested. It can be assumed that it was imagination, the desire to understand and explain that attracted attention to mental phenomena in antiquity, supported and continues to stimulate it today. As for the mystery of this phenomenon, it lies in the fact that so far we know almost nothing about the mechanism of imagination, including its anatomical and physiological basis. Even in which part of the brain imagination is localized, science is not known.

Thanks to the imagination, a person creates, intelligently plans his activities and manages them. Almost all human material and spiritual culture is a product of the imagination and creativity of people, and we all already know quite well what significance this culture has for the mental development and improvement of the “homo sapiens” species. Imagination takes a person beyond the limits of his momentary existence, reminds him of the past, opening the future. With a rich imagination, a person can "live" in different times, which no other living creature in the world can afford. The past is fixed in images of memory, arbitrarily resurrected by an effort of will, the future is presented in dreams and fantasies.

Imagination helps a person in many ways in those cases of life when practical actions are either not possible, or difficult, or simply inappropriate (useless).

Imagination differs from perception in that its images do not always correspond to reality, they contain elements of fantasy, fiction. If the imagination paints such pictures for the consciousness, to which nothing or little corresponds in reality, then it is called fantasy.

1.3. Physical assessment of the environment.

Physics, in turn, is an exact science, therefore, in order not to delve into the controversy - fantasy is more important and necessary or reality, let's say that reality also plays an important role. A person sees everything around him in a reduced size, perceives only the sun's rays. It is known from biology that the eye is an organ of imperfect accuracy. Muscles of different strengths affect the eye, the retina has some curvature, both eyes are located horizontally, they have blind spots, and in general: the area of binocular vision in a person is small and he sees only in front of him, while a fly with its faceted eyes can see from behind and perceive more than 300 images per second!

Therefore, trust in such a variant of subjective assessment as "by eye", especially in physics, is not justified. Therefore, what is actually there, we perceive with distortions.

Chapter II . Features of the human imagination.

2.1. Imagination and reality

Imagination can be of four main types: active, passive, productive and reproductive. Faced with optical illusions, people without will deceive their minds, most often without even noticing it, and only resorting to the help of measuring instruments, they discover a discrepancy. Some time ago you were able to verify this. Look at figure 1: there are two sticks perpendicular to each other that intersect.

They are equal, but it seems that the vertical one is noticeably longer than the horizontal one. When observers were asked to draw actually equal sticks, the result differed from the real size by 33%! Images of passive imagination arise in addition to the will and desire of a person. But no fantasy is capable of inventing something that would not be known to a person, therefore: a person will consciously depict these sticks with a discrepancy of 33%, since he is sure that he is right and, even learning about a mistake, he will continue to make it , because it is in this form that they will be equal for him, moreover, this is an inveterate habit, which is almost impossible to get rid of.

As it was written above, it is thanks to the imagination that a person is able to create. But most often, the impulse of the creative process is active (by willpower), productive (conscious construction without reproducing what was created before ...) and reproductive (copying) types of imagination.

Much less often, passive imagination serves as such an impetus. Although it is known from the example of poetry, how the author involuntarily composes poetry, while striving to find the possibility of recording a new rhyme so as not to lose it. They say there is inspiration. In addition, the creative process, starting, as a rule, with an effort of will, i.e. from the act of imagination, gradually captures the author so much that the imagination becomes spontaneous, and it is no longer he who creates images, but images own and control the artist, and he obeys their logic.

2.2. Impossible figures are a feature of the imagination.

Therefore, the goal was to tell in more detail about a special kind of illusions and drawings: impossible figures and objects. The first impossible figure was created in 1934 by the Swedish artist Oskar Reuterswerd, depicting nine cubes in a special order (Fig. 2).

Peru Reuterswerda owns hundreds of variants. Three of them, including the cubes, were reproduced on a series of postage stamps issued in Sweden in 1982.

But perhaps the most famous of the impossible figures is the Penrose triangle (Fig. 3) published in 1958 in the British Psychological Journal by L. and R. Penrose.

They were based on a drawing by Reuterswerd. Looking closely at the triangle, we see that all three corners of this frame are straight, although it is clear that this cannot be. Here the rules we learned from childhood for depicting objects on a flat sheet of paper come into conflict with each other.

Adding fuel to the fire of the conflict between imagination and common sense is a drawing showing how the Penrose triangle can be made (Fig. 4).

As you can see, all you need for this is three wooden cubes and three sticks connected with sticks, as shown here, or with glue - and you're done!

Despite the simplicity of this triangle, it is possible to draw an impossible figure with fewer elements. Pay attention to this example of two bars (Fig. 5): on the right they lie on top of each other, and on the left - next to each other.

Having understood the principle of drawing simple impossible figures, you can draw more complex ones. Pay attention to this trapezoid (Fig. 6) - the principle of its drawing lies in the fact that its corners, if you look closely at them, are actually straight, similar to the corners in the impossible Penrose triangle.

And this cube (Fig. 7) is remarkable in that, if we recall its definition from geometry - all faces are equal to each other, this is not a cube at all, although the three middle faces that form the inverted Mercedes icon are equal, but the rest visible to us six sides, no. Here is an explanation for its impossibility.

Figures are known in which one element or a gap between elements disappears. They are close by the principle of drawing to the "one and a half block" drawings. Try to count the number of bars in this figure 8.

It is wrong to assume that "impossibility" is the lot of only geometric figures. Such effects were used and continue to be used by artists of surrealism, futurism and a number of other trends in painting.

Here is a product of the imagination of a certain artist (Fig. 9). This is an impossible tuning fork, from which a completely normal shadow emanates, from which quite normal, sound waves depart.

As you know, a smaller telescopic tube, the so-called finder, is often attached to the telescope, which allows you to more or less accurately point the main telescope to the part of the sky that we want to examine. Then how many additional telescopes are attached to this telescope (Fig. 10).

And, if you find them, where, in fact, is the main pipe!?

The Devil's fork (Fig. 11) was named as such by one of those who saw the "phenomenon" of the transformation from a quadrilateral with two outgoing rectangular parallelepipeds into a three-pronged fork with cylindrical ends.

But in fact, the principle of the Devil's fork is very simple - elementary. As you know, a part of a rectangular quadrilateral has only three faces on the side, while a cylinder, when viewed from the side, has two completion lines, therefore three plus three and divided by two - three cylinders.

According to the principle of the "Devil's fork", a lot of pictures are drawn on other topics and plots. For example, in this picture (Fig. 12), three people on the left are carrying three pipes, and two on the right are helping them carry two ... bars.

And in this picture (Fig. 13) the properties of the shadow and, of course, the effect of the disappearance of the element are used.

Chapter III . Optical illusions.

3.1. Optical illusions are an integral part of human life

A number of very important features of human vision allowed us to create images on a plane, but to perceive in volume. But this is an optical illusion. We would perceive the mixture of colors on the canvas as spots, and the picture would be for us a lot of blots on paper. Therefore, what we see in the picture is only an illusion of everyday life.

3.2. History of discoveries.

The first study in the field of optical geometric illusions was made by the physicist Oppel. Then there were more than 200 scientific papers on this topic, where all the authors tried to find their own explanation of this problem. Each scientist has been looking for his theory on this matter for a long time, however, apparently, no one has guessed that these illusions are more the rule than the exception and that these features of vision and perception leave their mark on our entire daily life, and not just on individual pictures. The ancient Greeks were very familiar with the peculiarities of vision - the distance between the columns of the Parthenon was different, and the audience was perceived as the same - an illusion. But one architect, closer to our time, designed the building with very high accuracy, and when it was built, it turned out that if viewed from the front, then the roof line is concave outward, if from the side, then inward. All distances were clearly measured, but no inaccuracies were found - features of human vision. Illusion. As one of the tasks of this scientific work, we tried to classify the most famous optogeometric illusions and explain the possibility of the appearance of some of them.

3.3. Classification of optical illusions.

3.3.1. Intersection illusion.

Let's turn again to the picture, which shows the horizontal and vertical lines (Fig. 1). As noted, the horizontal line seems to be much shorter than the vertical one, if you do not resort to the help of measuring instruments. One of the reasons for this error is the intersecting vertical line. The reason for our error is that a person has binocular vision - the middle of the overall picture perceived by the eyes; as you move away from the middle of the gaze, vision ceases to be as clear as in the radius of the binocular. Therefore, a person’s gaze is “riveted” to the crossing line, and what is to the left and to the right falls beyond the radius of the clearest vision. The horizontal is divided in two, and therefore it seems smaller, falling into the weak flanks of the picture.

As a result, very large errors are obtained, but one consolation is that they arise only when the experimenter is content only with an estimate by eye, without resorting to the help of a scale ruler.

3.3.2. Illusion of "continuation-break".

Fig.14

The illusion that you are now observing (Fig. 14) has been known for over a hundred years. Arrows are drawn to the ends of two lines of equal length, to one - diverging in different directions, to the other - converging towards each other. The right line appears shorter than the left. This illusion is most pronounced if the arrows divide exactly in half, but the lower one seems to be much longer than the upper one. After the observer drew "really equal" lines, the discrepancy with reality was 33%. The thing is that the direction arrows serve in one case as a false lengthening, and in the other as a shortening. The arrows pointing towards each other are the "continuation" of the vertical line, and the arrows going in different directions, on the contrary, are the "limiters" of the length.

3.3.3. Illusion of curvature.

With the curvature of straight lines, there are many different illusions. In this picture (Fig. 15), because of the background, it seems that these lines are not parallel lines at all, but arcs.

Fig.15

In this case, the visual distortion is primarily related to the background. The fact is that, if you notice, it’s not two lines that come to the fore, but a spot with rays emanating from it. The spot "chains" binocular vision, and two lines go beyond it. The eyes have another very interesting property: straight lines under the variegation of colors become arched. Pay attention to this picture: it shows a straight line through each vertical curve, but under the influence of black and white zigzags and the alternation of curves and straight lines, it seems that there is nothing straight here.

It is known that black and white colors can cause many illusions in a person - this is how the retina is arranged. Therefore, there are many ways to play with visual impairments. In this picture (Fig. 16), the impression of curved horizontal lines is created because the black and white squares are offset from each other.

In fact, the horizontal lines are parallel.

3.3.4. Irradiation.

It has been known for more than a century that an image appears on the retina of the eye, consisting of light and dark areas, light from brightly lit areas, as it were, flows into dark areas. This is called irradiation. You can observe such a consequence of the contrast in this figure 17.

At the intersection of white lines, between black squares, so-called flashes of gray are formed.

Dark objects always appear smaller than light objects of the same size. If we consider simultaneously a black circle and a white circle of the same size on a light background, then the area of the circle will seem to us 20% larger than the area of the circle.

People in dark clothes appear thinner than those in light clothes. The sun at sunset forms a "notch" in the horizon line.

Irradiation depends only on the imperfection of our visual apparatus.

3.3.5. External pressure on the dimensions of an object.

The human brain has one amazing property of comparison. So, speaking about the size of an elephant, we mentally compare it with other objects, and it seems to us gigantic. But few people have seen a blue whale in full size. But, if we compare the blue whale with the elephant, then the elephant will seem to the eye the size of a dog. This explains another type of visual illusion.

Look at these circles (Fig. 19). You can clearly see that the right circle is noticeably smaller than the left, but in fact it is not.

Both circles are the same size. And the fault of this illusion is the same comparison. The left object is surrounded by circles of a larger diameter than the left one, and because of this, it seems that the right circle is larger. In real life, a kindergarten teacher seems like a giant to a child, but children grow up and when the child becomes the same height as the teacher, he will no longer seem like that.

The triangle (Fig. 20) in this parallelogram has sides AB and AC equal, although under the action of external objects it seems that AB is longer.

Conclusion.

In this work, the features of the visual apparatus, due to which optical illusions arise, were considered and studied from the point of view of physics, biology and psychology. Articles on this subject have been found and read. In the work, attempts were made to classify optical illusions into several basic types. It was found that the fault of their occurrence is not only the features of the eye, but also the brain. Therefore, this problem cannot be studied one-sidedly, using only physics.

I would like to remind you once again: the distortion of vision, which was written above, is inherent in each of us. Therefore, the errors associated with them are inherent in both mere mortals and professional artists, architects and many others. Remember: our eye estimates of geometric quantities are directly dependent on both physical parameters and psychological characteristics.

Even in the most serious scientific papers and projects, one can make a mistake that can lead to terrible consequences, using even a small fraction of an estimate by eye.

Scientific literature.

1. Aksenova M., Izmailova S. Encyclopedia for children. Volume Biology. M.,

"Avanta +" 1994. p.29.

2. Perelman Ya.I. Entertaining mechanics. 1979, p.123.

3. Perelman Ya.I. Entertaining physics. M. 1981, p.73.

4. Ivanov P.S. Journal "Science and Life". M. 1989, No. 4, p.116.

5. Traitaka D.I. Biology. Reference materials. M., "Enlightenment" 1994,

6. Russell K., Carter F. Improve your intelligence. Minsk, Potpourri 1996, p.45.

1.Introduction 1

2. Concept of optical illusion 4

3. Types of illusions 5

4.History of discoveries 11

5. Conclusion 12

6. Literature 13

INTRODUCTION At present, despite the development of science and technology, a person continues to use his subjective assessments in all areas. Of course, if this concerns non-mathematical sciences, then there is nothing wrong with that, but when it comes to estimates, in case of an error in which irreparable things can happen, then one should forget about intuition and use measuring instruments. This, of course, applies to the so-called "by eye" assessment. The term "illusion" is very common. Unfortunately, our eye is not an accurate instrument in the world, and therefore it tends to make mistakes. These errors are called optical illusions. A very large number of them are known and they are not all of the same type, as well as the reasons for their occurrence. Here are two real-life cases: There is a mountain in California that local motorists say is magnetic. The fact is that on a small section of the road 60 m long at the foot of this mountain, unusual phenomena are observed. This section is sloped. If the engine of a car driving downhill is turned off, then the car rolls backwards, i.e. up the slope, as if obeying the "magnetic attraction" of the mountain. This amazing property of the mountain was considered to be established so reliably that even a board with a description of the phenomenon flaunts in the corresponding place on the road. There were, however, people who thought it doubtful that the mountain could attract cars. For verification, this section of the road was leveled. The result was unexpected: what everyone thought was a climb turned out to be a 2-degree descent. Such a slope can cause the car to roll without a motor on a very good highway. The illusion of sight also explains the stories of travelers about rivers in which water flows up the slope. I quote an extract about this from the book of one physiologist, Professor Bernstein, “External Senses”: “In many cases we tend to make mistakes in judging whether a given direction is horizontal, whether it is inclined upwards or downwards. Walking, for example, along a slightly sloping road and seeing at some distance another road meeting the first, we imagine the rise of the second road to be steeper than it really is. We are then surprised to see that the second road is not at all as steep as we expected. This is explained by the fact that we take the road along which we are going for the main plane, to which we attribute the slope of other directions. We unconsciously identify it with the horizontal plane, and then, naturally, we imagine the slope of the other path to be exaggerated. This is facilitated by the fact that our muscular feeling does not at all catch slopes of 2-3 degrees when walking. On the streets of Moscow, Kyiv and other hilly cities one often has to observe the illusion about which the physiologist speaks. Even more curious is another optical illusion that happens to be succumbed in uneven terrain: the stream seems to us to be flowing uphill! When descending along a slightly sloping road along a stream, which has an even smaller fall, i.e. flows almost horizontally, it seems to us that the stream flows up the slope. In this case, we also consider the direction of the road to be horizontal, since we are used to taking the plane on which we stand as the basis for judging the inclination of other planes. Therefore, in order for people to make fewer mistakes, unconditionally trusting their eyes, they need to take into account some features of their visual apparatus.

THE CONCEPT OF OPTICAL ILLUSION

An optical illusion is a representation of a visible phenomenon or object that does not correspond to reality due to the structural features of our visual apparatus. Simply put, this is a misrepresentation of reality. (It is important to note that this does not refer to inconsistencies that are associated with individual visual impairments, such as color blindness.)

Why do optical illusions occur? The human visual apparatus is a complex system with a well-defined limit of functionality. It includes: the eyes, nerve cells through which the signal is transmitted from the eye to the brain, and the part of the brain responsible for visual perception. In this regard, there are three main causes of the illusion:

1) our eyes perceive the light coming from the object in such a way that erroneous information comes to the brain;

2) when the transmission of information signals through the nerves is disrupted, failures occur, which again leads to erroneous perception;

3) the brain does not always correctly respond to signals coming from the eyes.

Often optical illusions arise for two reasons at once: they are the result of a specific work of the eye and an erroneous signal conversion by the brain.

By origin, optical illusions are divided into three types:

natural, or created by nature (for example, a mirage);

artificial, or invented by man (for example, the “levitation” trick or, as the people say, “flying lady”;

mixed, that is, natural illusions recreated by a person (for example, well-known illusion pictures, a mirage model).

There is a significant difference between natural and artificial illusions. If an illusion is invented by a person, then it necessarily has a constructive secret, and after communicating it to the observer, it largely loses its mystery. Natural and mixed illusions do not change the strength of their influence, regardless of whether the observer knows their secret or not.

It should be noted that optical illusions are not necessarily born as a result of the play of light and shadow. So, at the heart of the already mentioned “flying lady” illusion is an ingenious mechanical design.

TYPES OF ILLUSIONS

Illusions of sight

Optical illusions, or the algebra of the impossible.

It is known that our vision is imperfect and sometimes we see something that does not exist in reality. But the fact that the vast majority of people sometimes receive the same erroneous visual impressions speaks of the objectivity of our vision and that it, supplemented by thinking and practice, gives us relatively accurate information about the objects of the external world. On the other hand, the fact that different people in the process of visual perception have a different ability to make mistakes, sometimes see in objects what others do not notice, speaks of the subjectivity of our visual sensations and their relativity.

Speaking in general about the causes of visual illusions (errors, deceptions), one should, firstly, point out that sometimes they appear as a result of specially created, special conditions of observation, for example: observation with one eye, observation with fixed axes of the eyes, observation through a slit, etc. .P. Such illusions disappear when the unusual conditions of observation are eliminated.

Secondly, the vast majority of illusions of vision arise not because of the optical perfection of the eye, but because of a false judgment about the visible, so we can assume that deception here arises when comprehending the visual image. Such illusions disappear when the conditions of observation change, when the simplest comparative measurements are performed, and when some factors that interfere with correct perception are excluded.

Finally, a number of illusions are known, which are also caused by the optical imperfection of the eye, by certain special properties of the various analyzers involved in the visual process (retina, nerve reflexes).

Illusions of vision do not include optical tricks and mysterious ghosts created with the help of mirrors, projectors and other technical devices, as well as interesting optical phenomena sometimes observed in nature (mirages, northern lights). The appearance of the latter is due to the optical properties of the earth's atmosphere. In all these cases, our eye is mistaken because it is deliberately deceived either with the help of technical devices, or due to the special state of the medium between the eye and the object of observation. Also, the visual illusions that occur in some people at dusk and in the dark are not illusions of perception, when insufficient lighting makes it difficult for the eyes to work and creates a special mood and distortion of sensations as a result of myopia, hyperopia, color blindness and other defects of the visual apparatus that are not typical for most people.

Illusions associated with the structural features of the eye

Blind spot. The presence of a blind spot on the retina of the eye was first discovered in 1668 by the famous French physicist E. Mariotte. The fact is that the retina of the eye in the place where the optic nerve enters the eye does not have light-sensitive endings of nerve fibers. Therefore, images of objects that fall on this place of the retina are not transmitted to the brain and, therefore, are not perceived. A blind spot, it would seem, should prevent us from seeing the whole object, but under normal conditions we do not notice this. First, because the images of objects falling on the blind spot in one eye are not projected onto the blind spot in the other; secondly, because the missing parts of the object are involuntarily replaced by images of neighboring parts or the background surrounding this object (in the figure, the disappearing figure is replaced by a white background).

Irradiation. The phenomenon of irradiation (in Latin - incorrect radiation) consists in the fact that light objects on a dark background seem to be more enlarged against their real sizes and, as it were, capture part of the dark background. When we examine a light surface against a dark background, due to the imperfection of the lens, the boundaries of this surface seem to move apart, and this surface seems to us larger than its true geometric dimensions. In the figure, due to the brightness of the colors, the white square seems much larger relative to the black square on a white background.

Illusions when an object moves

When the object of observation moves, a number of visual illusions are also encountered, which are due to some properties of our visual apparatus. For example, if a circle with a colored sector is rotated, then the whole circle seems to be colored to us. This can be explained by the ability of our eye to retain a visual impression for a fraction of a second, although the visible object has already disappeared from view.

There is an illusion that can be called the Plateau spiral, or, to put it simply, the spinning top effect. If a disk with a spiral (top) is rotated clockwise, then after a long fixation of it with the eye, we get the impression that all the branches of the spiral are being pulled towards the center; when the spiral rotates in the opposite direction, we see the divergence of the spirals in the opposite direction from the center to the periphery. If, after a long examination of a moving spiral, we look at stationary objects, we will see their movement in the opposite direction. So, for example, if, after a long observation of the terrain from the window of a moving train or of water from the window of a moving steamer, we shift our gaze to stationary objects inside the train or steamer, then it will seem to us that they are also moving, but in the opposite direction. These illusions are associated with successive moving images.

Cinematography is based on the property of our eye for 0.1 seconds to “see” what has already disappeared: when changing 24 frames per second and when the projector window is blocked at the moment of changing the frame with a special screen (obturator), our eye does not notice this change and perceives not the movement of the tape, but the slower movement of the figures projected onto the screen. Television also uses the law of visual impression. In this case, on the luminescent screen of the cathode-ray tube of the receiver, the electron beam, at a very high speed, seems to “draw” the image of the picture we see, moving along horizontal lines and shifting vertically from line to line. Due to the high speed of the electron beam moving from the top of the screen in lines to its lower border, we do not notice this movement, but perceive the image as a whole.

Illusions of color vision

The most important property of our eye is its ability to distinguish colors. One of the phenomena - the phenomenon of shifting the maximum of relative visibility during the transition from daytime to twilight vision - consists in the fact that with twilight vision (at low illumination) not only the sensitivity of the eye to perception in general decreases, but also that under these conditions the eye has a reduced sensitivity to colors of the long-wavelength part of the visible spectrum (red, orange), but it has an increased sensitivity to the colors of the short-wavelength part of the spectrum (blue, violet). The red poppy and cornflower in the picture in daylight seem to be close in brightness to each other. At dusk, the poppy seems completely dark, and the cornflower is lighter.

Sometimes when looking at colored objects, we also encounter visual errors or illusions. First, sometimes we mistakenly judge the saturation of a color by the brightness of the background or by the color of the surrounding objects. In this case, the laws of brightness contrast also apply: the color brightens on a dark background and darkens on a white one. Secondly, there is the concept of proper color contrasts, when the color of the object we observe changes depending on the background against which we observe it. Illusions of this kind we meet in the following forms. The black circle in the figure seems slightly reddish on a green background, when we cover the drawing with thin transparent paper, the illusory red color becomes even more noticeable (the sharpness of the borders is erased and the difference in the brightness of the field and background is reduced, and thus enhances the manifestation of the effect). Similarly, a black circle on red will appear greenish, on a violet-blue background greenish-yellow, and on blue a copper-red.

Another kind of color illusion is that some colors are perceived as "protruding" and others as "receding". This fact is clearly illustrated in the figure below. Looking at the figure on the left, we tend to think that it is a truncated pyramid with its apex facing us. But on the left, we would rather imagine a tunnel with an outlet in the distance. "Protruding" colors usually appear to be red-orange-yellow (or "warm") colors, while "receding" colors appear to be green-blue (or "cold").

size illusions

Even in antiquity, people were confused by the fact that the moon and sun appear larger on the horizon than when they are high in the sky. This optical illusion is called the illusion of the moon. The whole effect is that the presence of the earth gives the impression that the moon at the horizon is further away than the moon at its zenith, since the filled space between the observer and the horizon gives the impression of a greater extent than the unoccupied space between the observer and the sky above. Therefore, it seems to us that the moon on the horizon looks larger than the rising moon.

We are generally accustomed to the fact that all objects receding to the horizon decrease on the retina in their linear dimensions: people, trains, clouds, planes ... “If we saw an airplane rising above the horizon beyond a distant village, the same size as we see it above head, it would appear larger than the village itself and would probably represent a terrifying sight,” writes the famous English physicist William Bragg in his book “The World of Light”. So is the moon: approaching the horizon, it would have to decrease in size, like an airplane, experience imperiously requires this. And since “near the horizon” means to our “unconscious inferences” that the moon is further away than when it was overhead, something must be done about the fact that the angular size of the disk is angularly constant. So it turns out psychologically that the disk has become larger. Otherwise, moving away, it could not have remained the same angular size. And we see the moon huge!

portrait illusions

Many have seen the so-called mysterious, as if alive, portraits that are always looking at us, following our movements and turning their eyes to where we are moving. This is due to the fact that the pupils of the eyes in the portrait are placed in the middle of the section of the eyes. This is how we see the eyes looking at us, but when the eyes look to the side, past us, the pupil and the entire iris seem to us to be not in the middle of the eye, but shifted to the side. When we move away from the portrait, the pupils, of course, do not change their position - they remain in the middle of the eyes, and since we continue to see the whole face in the same position in relation to us, it seems to us that the portrait has turned its head and is following us .

HISTORY OF DISCOVERIES

CONCLUSION

90% of information enters our brain through the eyes. Even if a person lives without rose-colored glasses, he will not always be able to realistically assess the situation he has seen. This is how our eyes work. Knowing the features of vision, a person can analyze the resulting image, understand when his eyes are deceiving him, and when the image is completely real.

Such knowledge can make life much easier by eliminating the troubles associated with visual deceptions. They will help to better understand some natural phenomena, the devices of some objects (traffic light).

Do not forget that optical illusions accompany us throughout our lives. Therefore, knowledge of their main types, causes and possible consequences is necessary for every person.

LITERATURE

1. Wikipedia

2. Textbook on physics grade 11. Publishing house Enlightenment.

optical illusions

Or an optical illusion

Performed:

9th grade student

Rakhmanova Zina Andreevna

Introduction__________________________________________________ 3

Some types of optical illusions ______________________ _ 4-10

Experimental studies of the perception of illusions_________ 11-13

Creating photos with optical illusions _____________ 14

Conclusion ____________________________________________ 15

References _______________________________________________16

Annex_______________________________________________ 17-28

INTRODUCTION

The expression "deception" in life is very common. Unfortunately, our eye is not an accurate instrument in the world, and therefore it tends to make mistakes. These errors are called optical illusions. Simply put, this is a misrepresentation of reality. A very large number of them are known, and all of them are not different, as well as the reasons for their occurrence.

Often what we see is deceptive, and much is not at all what it seems at first glance. Even the simplest things can be fraught with the most unexpected discoveries, you just need to take a closer look.

But should we trust everything we see? Is it possible to see what no one has seen? Is it true that stationary objects can move? What is the variety of optical illusions? I really want to find answers to all the questions posed, so I decided to conduct a study "Illusion" and look into this issue.

Target: which I set for myself in the study - Find out what underlies the optical illusion - miracles or science?

To achieve this goal, it is necessary to solve the following

Tasks:

1. Pick up material about the types of optical illusions, the reasons for their occurrence.

2. Conduct a study, during which it will be possible to determine the percentage of objectivity in the perception of the object by students in the 9th grade and teachers.

3. Learn to manage illusions.

Object of study - optical illusions.

Subject of study Causes of optical illusions.

Research hypothesis Illusions are based on ordinary natural phenomena.

Some types of optical illusions.

Studying this issue in the encyclopedic literature and on the Internet, I found out that in translation from Latin the word "illusion" means "mistake, delusion". This suggests that illusions have long meant some kind of malfunction in the visual system. In the second half of the 19th - early 20th centuries, a lot of test images were created that indicate the errors of what we see on them. OPTICAL ILLUSION is an impression of a visible object or phenomenon that does not correspond to reality, i.e. optical illusion.

Optical illusions are divided into three types:

natural, or created by nature;

artificial, or man-made;

Mixed, that is, natural illusions recreated by man.

Types of optical illusions:

natural optical illusions

Mirages

Mirage is a play of light rays. The word "mirage" comes from

French word and means “to reflect, as in a mirror”, and in the role

"mirrors" protrudes ... air. Mirages are usually divided into three classes.

The first class includes inferior mirages - an inverted image

items. It turns out that the air consists of layers that have different

temperature and density. When the rays pass from one layer to another, they begin to refract, and if the temperature difference between the layers is large, then the rays

generally begin to be reflected, while creating illusions that

are called mirages. So, for example, in the desert, the sand is heated

under the sun, the lower layer of air heats up and begins to reflect

objects like a mirror. Inferior mirages can also be seen on

hot sun asphalt road.

The mirages of the second class include superior mirages. They are less common and more picturesque than the lower ones. An upper mirage occurs when the layers of air near the earth are much colder than the upper ones: the image breaks off the ground and hangs in the air, sometimes it is upside down. An upper mirage can describe an arc and return to the ground after hundreds of kilometers. (Ideal conditions are created above the sea for formation upper mirage. Therefore, sailors often see ships hanging in the air, and even ships far beyond the horizon. There are also side mirages. They are similar to the lower ones, only in

In this case, everything is reflected not from the earth, but from the heated by the sun's rays

walls. Mirages of the third class or Fata Morgana are a mysterious phenomenon,

which cannot be explained by any laws of physics.

Thousands of tourists and residents of the eastern Chinese city of Penglaive

2006 witnessed a rare phenomenon - a huge mirage

The fog hanging over the shore created the illusion of an image of the city from

modern high-rise buildings, wide city streets, 7

noisy cars and crowds of people that were clearly visible.

The mirage lasted several hours, and before its appearance 2 days were torrential

rain. One of the best places in the world to see mirages is

Alaska. The worse the cold in Alaska, the clearer and more beautiful they appear in the sky

blind spot

In the process of research, I learned the amazing features of the structure of our eye. So, for example, there is a blind spot of the eye, discovered by the French physicist Mariotte in 1668. The blind spot is the place on the retina where the optic nerve enters the eyeball. Mariotte's drawing is known for finding a blind spot. If you look at the cross with your right eye (the left eye should be closed), bringing the drawing closer or further away from the eye, there comes a moment when the black circle is not visible. It turns out that because of the blind spot I should see the world around me with gaps? It turns out not! We have two eyes, so when an image enters the blind spot of one eye, the other eye sees all the details.

Consider how our vision works. A beam of light bouncing off a

object hits the cornea and passes through the pupil. Behind the pupil

the lens is located, similar to a transparent lens, which 8

refracts light and focuses it on the retina. Next is the optic nerve

transmits a signal to the occipital lobe of the brain and the person sees

image. This means that vision controls not only the eye, but also the brain.

Therefore, when they talk about "deception of the eye" it would be more correct

to say that we are actually being deceived by our own brain when

analyzes what he sees.

At this stage of the research, I made another discovery for myself -

the invisible man from the novel by the English writer HG Wells could not

see! His pupil and lens are transparent, so the rays through his eyes

an invisible person pass without obstacles and cannot gather into one

point to create an image on the retina. So the person is invisible.

must be blind.

size illusion

One of the most famous illusions of size perception is the Muller-Lyer illusion. Looking at this picture, many will say that the segment with arrows outward is longer than the segment with arrows pointing inward. In fact, the segments are equal.

Two perfectly equal circles in the middle are perceived as different in size depending on whether they are surrounded by larger or smaller circles.

The illusion with circles is explained by the action of the law of contrast, the object will appear larger than its real size against the background of small objects, and vice versa.

Another example of this type of illusion is the Ponzo illusion. It is obvious to everyone that the far segment is much larger than the near one. However, in this case they are equal. The illusion is created due to a mistake in our brain, because it is used to the fact that the farther the object, the smaller it is.

Distortion of the shape of objects.

Parallel lines will be perceived as non-parallel when viewed against the background of mutually intersecting oblique lines. The circle loses its regular shape when viewed against a background of curved lines.

This type of illusion finds its explanation in the fact that the pronounced features of the background affect the perception of objects located against this background.

Re-evaluation of vertical lines. Of two lines of the same size, the vertical one is always visually perceived as much larger than the horizontal one. In connection with this illusion, the height of objects seems to us greater than its actual value. (The woman on the right appears shorter and fatter.)

Moving illusions.

A still image appears to be moving. The same rotating image can rotate in different directions.

Geometric illusions create huge opportunities for artists, photographers, fashion designers. However, engineers and mathematicians have to be careful with drawings and reinforce the "obvious".

Illusion of color perception

The most important property of our eye is its ability to distinguish colors. But even here the illusions managed to deceive me. In the picture, among the stripes of blue and yellow, I saw two shades of red and two shades of green, although in reality there is only one red and one green. The error arose due to the brightness of the background and the color of the surrounding objects.

In the Goering grating, at the intersection of the white stripes, except for the intersection where I fixed my gaze, small gray spots were visible. It turns out that you can see something that is not there!?

Illusion of movement

Illusions of movement are the most impressive and the most difficult to explain. You look at stationary objects, and they begin to move. The same rotating image can rotate in different directions. Most of the illusions of movement are built on the regular repetition of fragments of different brightness or color. Peripheral vision plays a leading role in the illusion of movement. Try bringing your finger to your temple. You won't see him. But it is worth moving a finger, and the movement will be noticed, although the visual system will not be able to recognize what is flashing there. The well-known creator of motion illusions A. Kitaoka conducted research and found out interesting facts. It turns out that some people cannot see the illusion of movement (according to some estimates, there are about 5% of them).

Another fact is no less interesting: older people more often than young people do not see the movement.

artificial illusions

Dual images

Dual images are images in which a person selects for himself either a background or a figure, depending on his perception of the picture.

Images are shifters

Whatever one may say, no matter how you flip the reversed images, the pictures do not change places.

Impossible figures and objects

There is a huge class of so-called "impossible figures" that are erroneously or deliberately drawn with errors, resulting in funny visual effects.

Pattern recognition

Illusions of pattern recognition are characterized by the fact that sometimes it is very difficult to determine what is depicted on the image.

Sometimes the main drawing itself does not allow you to see an additional image, in other words, it does not allow you to recognize the image. If, nevertheless, the image is recognized, it can already be seen without difficulty during subsequent viewing of the pictures.

Mixed illusions

This is perhaps the largest section of illusions. It includes well-known illusion pictures, various models, and naturally this “deception” is created by a person. A striking example of a mixed optical illusion is the stunning drawings on the pavement, which look very impressive from a certain viewing angle!

Application of optical illusions

Optical illusions are not new in architecture. The architects of ancient Rome had a knowledge of optics, which was quite enough to create magnificent optical illusions on floors using the mosaic technique.

In Odessa, there is a very popular attraction "Witch's House". The optical illusion of a flat house is created due to the fact that the side walls of the house are built at an acute angle. Looking at the customs house in Australia, it seems that the floors are expanding and narrowing, although each floor of the house is the same height.

Illusions in the circus are created through the use of special equipment - a double bottom, special springs, hidden partitions, a certain installation of mirrors. Ingenious devices carry out all sorts of "mysterious" disappearances and appearances of things and people, serve to hover objects and people in the air, sawing them or burning them.

The fashion world is a world of visual illusions. In the history of the costume, one can trace how the waist was “narrowed” with the help of very wide skirts, the legs were made longer with the help of an overestimated waistline. Vertical lines and details of clothing (stripes, arrows on trousers, long scarves, high heels) visually slim and increase growth. Contrasting vertical stripes run down the outer sides of the garment for a fitted silhouette. Horizontal lines (seams, pockets, frills, shoe straps) are fatter. The cage increases the volume, and the circles give the forms roundness. A suit in one color gives the appearance of tallness, looks more refined and elegant, and clothes with bright color spots make them look fuller.

Experimental studies of the perception of illusions

I gave examples of several types of optical illusions. The next step is a small experiment with students from our school. Will they succumb to the illusion of visual perception? I will show them, one by one, optical illusions and ask them to answer my questions.

20 students of the 9th grade took part in the experiment:

1st drawing

Which of the circles located in the middle is larger?

LEFT RIGHT

A) left more

B) right more

C) the same

Answer options for the 1st figure	Number of students	% of students
BUT	8	40%
B	6	30%
B(correct)	6	30%

2nd drawing

Count the number of legs on the elephant shown in the picture:

Answer options for

3rd drawing

Number of students

% of students

65%

35%

3rd drawing

The figure shows two blue lines. Which one is longer. Left or right?

A) the left one is longer

B) The right one is longer

B) the same

Answer options for the 2nd figure	Number of students	% of students
BUT	9	45%
B	4	20%
B (correct)	7	35%

Survey among teachers

Experience #1

Answer options for 1st drawing	Number of teachers	% of students
BUT	4	67%
B	2	33%
B(correct)	0	0%

Experience #2

Answer options for the 2nd figure	Number of teachers	% of students
BUT	4	67%
B	2	33%

Experience No. 3

Answer options for the 3rd figure	Number of students	% of students
BUT	2	33%
B	2	33%
B (correct)	2	33%

RESEARCH CONCLUSIONS:

I conducted research among students of our 9th grade and teachers and determined the percentage of perception of illusions by schoolchildren and teachers. The experiment showed that we do not always see what is actually there, therefore, our hypothesis is correct. We came to the conclusion that the objects and phenomena that we see do not always correspond to reality and are true. The analysis carried out teaches us that one should not always limit oneself to only an estimate by eye, but one should connect logic and make measurements.

People cannot fully control what they see and are easily deluded. In my experiment, this is an average of 71% of students in 3 experiments.

And finally, I tried my hand at creating photos with optical illusions.

At first it may seem that an optical illusion is created easily, in fact it is, but before achieving impressive results, scientists spent a lot of time and effort studying the structure of the eye, its features, features of vision and the reaction of the eyes. But today, optical illusion is considered not only one of the research methods, optical illusions are considered useful for the development and natural training of the eyes, and more recently, optical illusions have been used in life. Mostly these are paintings, illustrations or photographs.

Photographs with optical illusions have recently become more and more popular, special exhibitions are being created, since these photographs are more related to art than to scientific activity.

I also decided to try myself in this art.

Photo of illusions of deceit.

Broken pencil in water

Complete experience

Place a pencil vertically in the middle of the bottom of an empty glass and look at it so that its lower end, the edge of the glass and the eye are on the same line. Without changing the position of the eyes, pour water into a glass. Why is it that as the water level in the glass rises, the visible part of the bottom increases noticeably, while the pencil and the bottom seem to be raised?

Position the pencil obliquely in a glass of water and look at it from above and then from the side. Why does a pencil appear broken at the surface of the water when viewed from above?
Why, when viewed from the side, the part of the pencil located in the water seems to be shifted to the side and increased in diameter?
This is all due to the fact that when passing from one transparent medium to another, the light beam is refracted.

Observation of the deflection of a laser flashlight beam when passing through a plane-parallel plate.

The incident beam, the refracted beam, and the perpendicular to the interface between two media, restored at the point of incidence of the beam, lie in the same plane; the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant value for two media, called the relative refractive index of the second medium relative to the first.

The refractive index relative to vacuum is called absolute index of refraction.

In the collection of tasks, find the table "The refractive index of substances." Please note that glass, diamond have a higher refractive index than water. Why do you think? Solids have a denser crystal lattice, it is more difficult for light to pass through it, so substances have a higher refractive index.

A substance with a higher refractive index n 1 is called optically denser environment if n 1 n 2 . A substance with a lower refractive index n 1 is called optically less dense environment if n 1 2

Well, how did I succeed?

Conclusion

So, the study of optical illusions has come to an end and we can conclude that the illusion is not a miracle, but a science. The hypothesis put forward at the beginning of the study was confirmed - almost all illusions are based on ordinary natural phenomena. In the process of work, three main causes of optical illusions were found:

1. The laws of physics - refraction and reflection of rays create illusions,

which are called mirages.

2. Features of the structure of the eye allow you to see the illusion of perception

colors and illusions of movement, the phenomenon of irradiation and astigmatism, and,

of course, a blind spot.

3. The study showed that vision controls not only the eye, but also

brain. Optical illusions are a trick of our brain, and vision is here

is only a mediator who transmits this deception.

The fact that not all illusions today have their own scientific explanation may indicate that human vision has not been sufficiently studied.

The knowledge gained in the process of research and the accumulated facts made it possible to learn how to create optical illusions and control them. It would be interesting to make a "Corner of Illusions" in the class, where the children would get acquainted with the basics of physics, conduct various experiments and studies, bring and demonstrate their inventions. As the first exhibits of the Corner of Illusions, I offer an album of optical illusions made by me. To date, in the study of illusions, there are still many secrets that are waiting to be discovered.

Bibliography

1. Perelman Ya.I. "Entertaining physics"

2. Internet resources

3. Explanatory dictionary of the Russian language S.I. Ozhegov

Try to imagine that the evolution of life on the planet went a different way and animals (including you and me) could not acquire such a feeling as sight. Does not work? No wonder - we are so used to relying on our eyes that we cannot even imagine what the world around us would be like without an optical component. For all the importance of vision, it is not so perfect - say, some combinations of signals are able to “outsmart” the brain (as you know, we “see” with neurons, not with our eyes), forcing a person to get confused in the size of objects or guess “movement” in a static image . Now, attention! Sit comfortably, "turn off" all senses except vision and focus on the screen - we will talk about optical illusions.

Classic optical illusions

The history of optical illusions has more than one thousand years, back in 350 BC, Aristotle wrote: "Our feelings can be trusted, but they are still easy to deceive." The great thinker noticed that if you look at a waterfall for a while, and then look at a motionless mountain slope, it may seem as if the rocks are moving in the opposite direction to the stream. Modern researchers call this optical phenomenon the motion aftereffect or the waterfall illusion.

When we observe the flow of water, part of the neurons in our brain adapt to the unidirectional movement of light signals, as a result, looking after the waterfall at a static object, we continue to “see” movement for some time, only in the opposite direction.

Illusion of Perception of Relative Sizes

Ebbinghaus illusion

In the 19th century, an active study of the properties of perception and the characteristics of the human senses began. It was then that researchers developed optical illusions, which are now considered classic, in the first place - the Ebbinghaus illusion.

Even if you are not too interested in the history of psychology, you are probably familiar with it, take a look at the picture. Of course, you understand that the sizes of the orange circles are the same, since you have seen such illusions a thousand times, but your eyes still lie to you - for a split second there is a feeling that they are still different. The human brain determines the size of objects and images based on the size of adjacent objects and inevitably falls into a trap - against the background of large black circles, orange seems smaller than next to small circles.

Illusion of depth perception

At the beginning of the 20th century, the Italian psychologist Mario Ponzo was one of the first scientists to demonstrate to the world that the perception of the size of objects is influenced not only by adjacent objects, but also by the depth of the background. The Italian developed the classic illusion that now bears his name.

The Ponzo illusion looks very simple - two identical horizontal lines are located between two inclined lines, while one of them is perceived as longer. The slanted lines create perspective, the brain thinks that the top horizontal line is "farther" than the bottom one and corrects for "distance" - this creates a curious effect.

"Magic" Muller-Lyer lines

Another textbook optical illusion that is over a hundred years old is the Muller-Lyer illusion. Its essence is also quite simple - the figure shows lines with arrows at the ends, the one framed by the “tails” of arrows seems to be larger.

Scientists are still arguing about the mechanism of the appearance of an illusion, the following interpretation is currently the most popular. Three converging lines are interpreted by the brain as part of a three-dimensional object, while the lines that form the “point” are perceived as a closer object (say, the corner of a building when viewed from the outside). The "tail" arrows, in turn, create the illusion of a distant object ("corner of the room"). As with the Ponzo illusion, the brain "compensates for distance" to the object, causing the lines to appear different.

The riddle of Helmholtz

Surprises to the brain are presented not only by converging lines, but also by parallel vertical or horizontal ones. At the end of the 19th century, the German physicist and physiologist Hermann von Helmholtz showed that a square drawn with horizontal lines looks wider and lower than exactly the same, but made up of vertical lines.

The phenomenon discovered by Helmholtz is widely used in the production of clothing, however, contrary to a common misconception, horizontal stripes on sweaters and dresses do not “full”, but on the contrary, they visually make the figure narrower and taller. You'll often find advice in fashion magazines like, "Wear vertical stripes to look slimmer," but science mercilessly refutes this. Take a look at the Helmholtz illusion and see for yourself that the effect is just the opposite.

It is worth noting that this optical illusion has been studied far and wide, but scientists cannot yet come to a consensus on the mechanisms of its occurrence.

Classical early illusions turned people's ideas about the world around them - as it turned out, "believing your eyes" is far from always possible. Nicholas Wyed, a specialist in the history of optical illusions from the University of Dundee (Scotland), is sure that optical illusions played a significant role in the study of the properties of perception: “Creating illusions, scientists realized that even understanding the mechanism of the eyes does not give a holistic view of the nature of vision.” Wade notes that the pioneers of creating optical illusions made attempts to unite them under one general theory, but they were unsuccessful. As it turned out later, the reactions of the human brain to optical illusions are much more complex and diverse than researchers saw at the turn of the 19th and 20th centuries.

Illusions in the 20th century

In the "age of wars and revolutions" humanity has witnessed many breakthroughs in understanding the nature of optical illusions. Advances in science and technology have given specialists the opportunity to take a different look at the problem. For example, the experiments of Thorsten Wiesel and David Hubel proved that different neurons are responsible for the perception of different areas of the visual field - for this discovery, the researchers were awarded the Nobel Prize in Medicine in 1981.

A little later, artists took up visual distortions - in the 1950s, a whole trend in art dedicated to optical illusions appeared, it was called op-art (from the English optical art - “optical art”). One of the founders of op art is the French artist and sculptor Victor Vasarely, whose works are often cited as vivid examples of optical illusions.

Illusions of our time

At the beginning of the 21st century, interest in visual distortions continues to grow - new scientific theories appear, with the help of which scientists try to explain the mechanisms of optical illusions. According to one of them, distortions occur due to the fact that the human brain constantly "predicts" the image in order to compensate for the delay between the event itself and the moment of its perception. For example, while you are reading this article, your brain is processing light signals coming from a computer monitor or gadget screen. It takes a certain amount of time, so you kind of see not the present, but the past.

Neuroscientist Mark Changizi believes that it is the brain's attempts to "anticipate" the picture that explains some of the visual distortions.

The experiments of Changizi and his colleagues at the California Institute of Technology show that none of the classical optical illusions contradicts this theory. Among the most illustrative examples of "prediction" of the image by the brain, Changizi names the famous Hering illusion. When a person moves forward, the objects they see move along radial lines, so the brain tends to perceive such images as a sign of movement in space. “These mechanisms work great in real life, but they also cause the brain to make mistakes when a person sees radial lines and at the same time remains in place,” the researcher notes.

The Necker Cube and other "whims" of the brain

The invention of magnetic resonance imaging has become a real gift for researchers of optical illusions - science has finally been able to understand, at least in general terms, what happens in the human brain when they are perceived. So, studying the brain activity of a person looking at the Necker cube, scientists concluded that the brain ambiguously perceives the depth of the image. Neurons seem to “argue” among themselves which picture should be considered “true”, as a result, the observer sees the cube in one position, then in another.

The situation is similar with another well-known optical illusion - the so-called Hermann grid. Take a look at the image - with peripheral vision you "see" gray dots at the intersection of white lines, but as soon as you focus on one "gray dot", it immediately "disappears". According to one of the most popular explanations among scientists for this phenomenon, there is a continuous “struggle” among neurons for processing dark and light areas of the image, which makes a person “notice” the flickering points.

The latest ideas about illusions

Thanks to modern research methods, humanity knows that different parts of the brain are responsible for the perception of color shades, shapes of objects and their movement in space, but how we get a holistic image remains a mystery in many respects. Enthusiasts are developing more and more new ways to deceive the eye, rethinking and supplementing classic illusions. Looking at them, we diligently "allow" our own brain to mislead us, and as a result, there are more questions than answers.

In our time, interest in the problem is so high that for the past ten years, experts have annually held a competition for the best optical illusion. For example, in 2014, this award was given to the dynamic Ebbinghaus illusion, which deceives the eye much more convincingly than the classic static version. According to the neurologist Suzanne Martinez-Conde, who is a member of the jury of the competition, due to the constant change in the size of adjacent objects, the effect of the new illusion is several times stronger than that of a still image proposed by Hermann Ebbinghaus.

Martinez-Conde acknowledges that much of the modern research on optical illusions is based on the work done by 19th century scientists. For example, Hermann Helmholtz was the first to understand that human eyes constantly make fast coordinated movements, the so-called saccades. To understand what it is about, close one eye and lightly press your finger on the lower eyelid of the other - the "picture" that your brain sees will immediately begin to move. In ordinary life, we do not notice these microscopic “twitches”, because the brain long ago learned to smooth the image, but when it encounters an unusual situation (mechanical impact on the eyeball), saccades manifest themselves in all their glory.

According to Suzanne, it is saccades that play a key role in the famous “Spinning Serpents” illusion, which was developed by the Japanese psychiatrist Akiyoshi Kitaoka. In experiments with Serpents, Martinez-Conde and her colleagues found that looking at the illusion fires the same neurons as when looking out the window of a fast-moving train, when it seems that the landscape is “driving past”, and not vice versa. At the same time, if with the help of some tricks the observer is forced to stop saccades, the illusion disappears.

The neurologist explains it this way: the appearance of movement in Spinning Serpents is created by a large amount of optical information entering different parts of the retina. A certain combination of light signals tricks the brain into perceiving a static image as dynamic. Saccades constantly update the “picture”, preventing the brain from adapting to it, but if they stop, the illusion of movement disappears after a while.

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