Is our eye always right?

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Is our eye always right?

In the “Quantum Laboratory” section in the 10th and 11th issues of our magazine for 1970, some experiments with vision were described. Their purpose is for readers to understand that not every visual sensation should be accepted as a physical reality. The human eye is a unique physical device that has amazing sensitivity and accuracy in perceiving the surrounding world. But it is also determined by the conditions of modern lighting.

Znamenty Russian literary hero of the 19th century. Kozma Prutkov advised: “If you see the inscription “Buffalo” on the word square, don’t believe your eyes.” However, our eyes often fail us even where all the inscriptions are made correctly.

During his student years, the author of these lines had the opportunity to give a scientific report on a seemingly completely anecdotal topic: “On the influence of penin on vision.” The point was, in part, that a person’s eyes, guided by the expectation of some experimental facts, quickly get tired and begin to see what is not in reality. So, it turns out that music helps restore normal sharpness and accuracy of visual perceptions.

Since the eye is the most important “tool” of a physicist, one must be well aware of the basic principles of its operation and the limits of its occurrence. This acquaintance can be significantly helped by the book by James Gregg “Experiments with Vision at School and at Home,” published in 1970 by the publishing house “Mir” *).

This book contains a description of four dozen experiments, which, as a rule, do not require any specialization of equipment and, if sufficiently realistic, can be completely reproduced at home. By consistently carrying out these experiments, you can learn a lot of interesting and sometimes unexpected information about the mechanism of visual perception of the surrounding environment.

Many of the experiments cited by Greg characterize various aspects of the eye, considered as an optical system: reflection and refraction of light by the human eye (experiments 2 and 4); live eye diffram

*) James Gregg, Experiments with vision at school and at home, M., Mir, 1970, 197 pp.

for - pupil (experiment 6); chromatic aberration of the optical system of the eye (experiment 8); field of view (experiment 13); visual acuity (experiment 15) - these are some of the experiments concerning the optical properties of the eye. This, so to speak, is the physics of our vision.

The processes through which we see the world around us are very complex and cannot be understood without taking into account the work of our nervous system, that is, without research into the physiology of vision. Rays of light passing into our eye separate the endings of the nerve fibers of the optic nerve. These signals enter our brain and, in many ways still incomprehensible to us, evoke pictures of what we saw. At the same time, it can correct and correct information received from our eyes, using the experience accumulated by a person.

Have you seen how hesitant the movements of the hands of a baby who has not yet learned to pronounce his first words are? How often does he try to grab a bright toy in a completely different place from where it really is. And all because maybe the child has not yet learned to help his eyes. This will take some time.

However, even in adults with the so-called normal eye, there are certain limits of exhaustion, beyond which the meaning deceives them, the information obtained with the help of the eye turns out to be unworthy. Many of the experiences in Gregg’s book help us navigate boundaries, to understand when we can trust our vision.

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information, and when it can deceive us, deceive us with false information. The influence of the background on the perception of an image (experiment 20); physiological image duplication (experiment 26); rivalry of figures, in which their images seem to be fighting with each other, suppression of the image and merging of colors (experiment 28); errors in estimating distances and sizes of objects (experiments 30 and 33) - all this makes us more cautious about what we see in reality.

It is not for nothing that the translator of the book follows the epigraph to one of the sections of the successor with the following story from a court chronicle of the 19th century:

• “State your complaint, Plaintiff.

• Your Honor, on a dark night I stood in my house at the wide open window. This man - the Defendant - came up to the window from the street - I couldn’t see him in the dark - and hit me in the face.

• Tell me, Plaintiff, if the darkness prevented you from seeing a person, then how were you able to identify him as the Defendant?

“From a strong blow, Your Honor, a pillar with a strong light flashed in my eyes, so that I clearly saw the face of this man.”

A few final ones dealt with various types of visual defects, like those that we talked about in the article by L. and R. Penrose “Impossible Objects,” published in the fifth issue of our magazine for 1971.

Not all questions related to Greg’s description of experiments can be answered today by the science of vision. In some cases, as the author warns, obligations have not yet been found at all. In other cases, the interested expert attaches importance to using his imagination and rummaging through other books to expand his position. The author himself partially encourages the reader to try to change the experimental conditions, test various changes and independently evaluate the best results. In a word, this book, as they say, “is not for the lazy minds.” It awakens interest, sharpens observation, and activates the work of thought. And this is its undoubted advantage.

The author prefaced his experiments with a short introduction, which describes the structure of the eye and the basic principles of its operation. The translator has supplemented the book with an extensive follow-up that expands the reader’s understanding of the physiology of vision. It contains many interesting facts about how plants and animals relate to light, how vision has changed and improved during the evolution of the animal world.

Unfortunately, the translation of the book into Russian is not done clearly enough. Especially many errors and inaccuracies were made when translating information from physical optics. The publisher should involve someone who specializes in this field in working on the book.

V. A. Leshkovtsev

(For a start, see page 50.)

2. Let’s use a formula, the validity of which can be verified using the method of mathematical induction or other methods. Here it is:
   $$n^3 + (n-1)^3 + (n-2)^3 + \dots + 1^3 = (1+2+3+ \dots + n).$$

The number of rectangles whose width from top to bottom is $m$, and from left to right is $k$, is
$$(n-m+1)(n-k+1).$$

The number of possible rectangles of all permissible sizes is exactly equal to
$$(1+2+3+\dots+n)(1+2+3+\dots+n).$$

3. There will be another triangle.

Indeed, three vertices out of nine can be chosen in $C_9^3 = 84$ ways. Of these, 8 degenerate triangles, 4 triangles equal to the one shown in figure 3, $a$ (in the task), 16 triangles of type 3, $b$, 4-type 3, $e$, 8-type 3, $e$, 4-type 3, $d$, 16-type 3, $e$, 8-type 3, $j$. Finally, there are 16 triangles equal to the one given in this topic. This exhausts all 84 possibilities.