Optical illusion. Optical illusions. Fields in physics. Interesting experiences in physics Optical experiments

Introduction

1. Literature review

1.1. The history of the development of geometric optics

1.2. Basic concepts and laws of geometric optics

1.3. Prism elements and optical materials

2. Experimental part

2.1. Materials and techniques of the experiment

2.2. Results of experiments

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 hollow glass prism and filled with air, with a refractive angle of 74º

2.3. Discussion of the results of experiments

List of used literature

Introduction

The decisive role of the experiment in the study of physics at the school meets the general principle of natural science, according to which the experiment is based on the phenomenon of cognition. Demonstration experiences contribute to creating physical concepts. Among the demonstration experiments, one of the most important places occupy experiments on geometric optics, which make it clear to show the physical nature of light and demonstrate the basic laws of the spread of light.

In this paper the problem of setting up experiments on geometrical optics using a prism high School. Select the most interesting visual and experiments on optics using equipment which can be acquired by any school or manufactured independently.

Literature review

1.1 The history of the development of geometric optics.

Optics refers to such sciences, the initial representations of which arose in deep antiquity. Throughout its long history, it has experienced continuous growth and is now one of the most fundamental physical science, enriched by the discoveries of new phenomena and laws.

The most important problem of optics is the question of the nature of light. The first ideas about the nature of the world appeared in the ancient century. Antique thinkers tried to understand the essence of light phenomena, based on visual sensations. The ancient Indians thought that the eye had a "fiery nature". Greek philosopher and mathematician Pythagoras (582-500 BC) and his school believed that the visual sensations arise due to the fact that "hot evaporations" proceed to objects. In its further development, these views took a clearer form in the form of the theory of visual rays, which was developed by Euclide (300 years BC. E.). According to this theory, vision is due to the fact that the "visual rays" expire from the eyes, which feel their body ends and create visual sensations. Euclidea is the founder of the exercise on the rectilinear spread of light. Applying to the study of light mathematics, he set the laws of reflection of light from the mirrors. It should be noted that to construct a geometric theory of reflection of light from mirrors, the nature of the origin of light does not matter, and only the property of its rectilinear distribution is important. The regularities found by Euclide are preserved in modern geometric optics. Euclidea was familiar and the refraction of light. At a later time, similar views developed Ptolemy (70-147. N. E.). They paid great attention to the study of the phenomena of the refraction of light; In particular, Ptolemy produced a lot of measurements of the angles of falling and refraction, but it was not possible to establish the refractive law. Ptolemy noticed that the position of the shone in the sky changes due to the refraction of light in the atmosphere.

In addition to Euclide, the action of concave mirrors knew other scientists of antiquity. Archhimeda (287-212 before and. Er) attribute the burning of the enemy fleet with the help of a system of concave mirrors with which he collected sun rays And sent to Roman ships. A certain step forward was made by EmPedocle (492-432 BC), which believed that the expirations of the eyes were sent from the glowing bodies, and expirations of the direction towards the bodies proceed from the eyes. When meeting these expirations, visual sensations arise. The famous Greek philosopher, the founder of atomistic, democritus (460-370 BC, er) completely rejects the idea of \u200b\u200bthe visual rays. According to the views of the democritus, the vision is due to the fall on the surface of the eye of small atoms emanating from the items. Similar views later adhered to Epicur (341-270. BC). A decisive opponent of the "theory of visual rays" was both the famous Greek philosopher Aristotle (384-322 BC), who believed that the cause of visual sensations lies outside the human eye. Aristotle made an attempt to explain the colors as a consequence of the mixing of light and darkness.

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

Arabic physicist Algazen (1038) in its research developed a number of optics issues. He was engaged in studying the eye, refraction of light, reflection of light in concave mirrors. When studying the refraction of the light of the Algazea, as opposed to Ptolemy, proved that the angles of fall and refractiveness are not proportional to what was a push to further research in order to find the law of refraction. Algazen is known for the magnifying ability of spherical glass segments. On the issue of the nature of the world, Algazen stands on the right positions, rejecting the theory of visual rays. Algazen proceeds from the presentation that rays come from each point of the luminous object, which, reaching the eyes, cause visual sensations. Algazen believed that the light had the final speed of distribution, which in itself is a major step in understanding the nature of light. Algazen gave the right explanation for the fact that the sun and the moon seem more on the horizon than in the zenith; He explained it to a deception of feelings.

Renaissance. In the field of science, the experimental method of studying nature is gradually defeated. During this period, a number of outstanding inventions and discoveries were made in optics. Francis Mavrolik (1494 -1575) belongs to the merit of a fairly correct explanation of the action of points. The Mavrolik also found that concave lenses are not assembled, but the rays dispel. It was found that the lens is the most important part of the eye, and concluding about the causes of the limanopiness and myopia as a consequences of the abnormal refraction of the light of the Mavrolik lens gave the correct explanation for the formation of the images of the Sun, observed during the passage of sunlight through small holes. Next, the Italians of the port should be called (1538-1615), which in 1589 invented the chamber-obscura - a modist of the future camera. A few years later, the main optical instruments were invented - a microscope and a visual tube.

The invention of the microscope (1590) is associated with the name of the Dutch Masters-Optics Zaharia Jansen. Spectatical pipes began to make approximately simultaneously (1608-1610) Dutch Optics Zakhariya Yansen, Yakov Mezius and Hans Lippershei. The invention of these optical instruments led in subsequent years to the largest discoveries in astronomy and biology. German Physics and Astronomom N. Kepleru (1571-1630) belong to the fundamental work on the theory of optical instruments and physiological optics, the founder of which he can rightly be named, Kepler worked a lot on learning the refraction of light.

The principle of a farm, named so named by the French scientist Pierre Farm (1601-1665), had great importance for geometric optics. This principle established that the light between two points applies to this path, to the passage of which spends the minimum of time. It follows that the farm, as opposed to Cartes, considered the rate of light propagation. The famous Italian physicist Galilee (1564-1642) did not conduct systematic work devoted to the study of light phenomena. However, in optics, it belongs to work, which brought wonderful fruits to science. Galilee has improved the auditorium and for the first time applied it to astronomy, in which he made outstanding discoveries that contributed to the rationale for the newest views on the structure of the Universe, based on the Heliocentric Copernicus system. Galileo managed to create a visual tube with increasing, frame 30, which many times exceeded the increase in the visual pipes of its first inventors. With her help, he discovered the mountains and craters on the surface of the moon, opened satellites for the planet Jupiter, discovered the starry structure of the Milky Way, etc. Galiley tried to measure the speed of light on earthly conditions, but did not succeed due to the weakness of the experimental funds that had for this purpose . From here it follows that Galiley has already had the right ideas about the final speed of light propagation. Galiley also observed solar spots. The priority of the opening of solar spots Galileem challenged the Jesuit's scientist Pater Sheiner (1575-1650), which was accurate observations of solar spots and solar torches using the visual pipe, arranged according to the Kepler scheme. Wonderful in the works of Sheiner is that he turned the visual tube into the projection device, putting forward the eyepiece more than it was necessary for a clear eye vision, it made it possible to get the image of the Sun on the screen and demonstrate with varying degrees of increasing to several persons at the same time.

The XVII century is characterized by further progress in various fields of science, technology and production. Mathematics gets significant development. In various European countries, scientific societies and academies are being created, uniting scientists. Thanks to this, science becomes the property of wider circles, which contributes to the establishment of international relations in science. In the second half of the XVII century, the experimental method of studying nature phenomena finally defeated.

The largest discoveries of this period are associated with the name of the ingenious English physics and mathematics of Isaac Newton / (1643-1727). The most important experimental opening of Newton in optics is the dispersion of light in the prism (1666). Exploring the passage of white light beam through a triangular prism, Newton found that white light beam decomposes to an infinite set of color rays forming a continuous spectrum. Of these experiments, it was concluded that the white light is complex radiation. Newton has also made reverse experience, collecting colored rays with a lenses formed after passing through the prism of the white light beam. As a result, he again received a white light. Finally, Newton has experienced color mixing with a rotating circle, divided into several sectors painted in the main colors of the spectrum. With a quick rotation of the disk, all the colors merged into one, creating the impression of white.

The results of these fundamental experiments, Newton laid the form of the color theory, which before that did not succeed in any of his predecessors. According to the theory of colors, the body color is determined by the rays of the spectrum that this body reflects; Other rays body absorbs.

1.2 Basic concepts and laws of geometric optics. The optics section, which is based on the representation of light rays as straight lines, along which the energy of light is distributed, is called geometric optics. This name is given to it because all the phenomena of the propagation of light here can be studied by geometric constructions of the ray, 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, the interaction of light with obstacles, the dimensions of which are sufficiently small, the laws of geometric optics are insufficient and it is necessary to use the laws of wave optics. Geometric optics makes it possible to disassemble the main phenomena associated with the passage of light through lenses and other optical systems, as well as with a reflection of light from mirrors. The concept of a light beam, as an infinitely thin beam of light, spread straightforwardly, naturally leads to the laws of rectilinear propagation of light and independent spread of light beams. It is these, laws in conjunction with the laws of refraction and reflection of light and are the basic laws of geometric optics, which not only explain many physical phenomena, but also allow calculations and design of optical instruments. All these laws initially were established as empirical, that is, based on experiments, observations.

Light scattering

Particles of a substance transmitting light behave like tiny antennas. These "antennas" take light electromagnetic waves, and transmit them in new directions. This process is called Ralea scattering named English physics Lord Rayleigh (John William Strett, 1842-1919).

Experience 1.

Put the sheet of white paper on the table, and next to it the flashlight so that the light source is located in the middle side of the paper sheet.
Fill two colorless transparent plastic glasses with water. With the help of a marker, we mark glasses with letters A and V.
Add a drop of milk into a glass in and stir
Fold the sheet white cardboard The size of 15x30 cm together with short ends and bend it in half in the form of a shala. He will serve you the screen. Install the screen opposite the lantern, on the opposite side of the paper sheet.

Dimmer the room, turn on the flashlight and notice the color of the light spot formed by the flashlight on the screen.
Put a glass and in the center of the sheet of paper, in front of the flashlight, and do the following: Notice the color of the light spot on the screen, which was formed as a result of the passage of light from the lantern through water; Look carefully on the water and note how the color of the water has changed.
Repeat actions, replacing a glass and on a glass of V.

As a result, the color of the light spot formed on the screen beam light of the lantern, on the path of which there is nothing but air, can be white or slightly yellowish. When the beam of light passes through clean water, the color of the spots on the screen does not change. The color of water also does not change.
But after passing the beam through the water, in which milk is added, the light spot on the screen seems yellow or even orange, and the water becomes a bluish shade.

Why?
Light, as well as electromagnetic radiation at all, has both wave and corpuscular properties. The propagation of light is waveled, and its interaction with the substance occurs as if the light radiation consists of individual particles. Light particles - quanta (otherwise photons) are cycling of energy with different frequencies.

Photons have properties both particles and waves. Since photons are experiencing wave oscillations, the photon size is accepted for the wavelength of the corresponding frequency.
The lamp is a source of white light. This is visible light consisting of all sorts of colors, i.e. Radiation of different wavelengths - from the red, with the highest wavelength, to blue and purple, with the shortest wavelengths in the visible range when the light oscillations of different wavelengths are mixed, the eye perceives them and the brain interprets this combination as white, i.e. No color. Light passes through clean water, not acquiring any color.

But when the light passes through the water, tinted with milk, we notice that the water has become a bluish, and the light spot on the screen is yellow-orange. This happened as a result of scattering (deviations) of parts of light waves. Scattering can be elastic (reflection), in which photons are faced with particles and bounce off them, completely just like two billiard balls bounce apart from each other. A photon is exposed to the greatest scattering when it encounters a particle is about the same as it is sized.

Small milk particles in water better dispel radiation of short wavelengths - blue and purple. Thus, when the white light passes through the water, tinted with milk, the feeling of pale blue color occurs due to scattering of short wavelengths. After scattering on the milk particles of short wavelengths from the light beam, it remains basically the wavelength of yellow and orange color. They go further to the screen.

If the particle size is greater than the maximum wavelength of the visible light, the diffused light will consist of all wavelengths; This light will be white.

Experience 2.

How does scattering depend on the concentration of particles?
Repeat experience using different concentrations of milk in water, from 0 to 10 drops. Watch the changes in the shades of water and light colors passed by water.

Experience 3.

Does the scattering of light depend on the light from the speed of light in this environment?
The speed of light depends on the density of the substance in which the light is distributed. The more the density of the medium, the slower the light spreads in it.

Remember that scattering of light in different substances can be compared by observing the brightness of these substances. Knowing that the speed of light in the air is 3 x 108 m / s, and the speed of light in water is 2.23 x 108 m / s, can be compared, for example, the brightness of wet river sand with the brightness of dry sand. At the same time it is necessary to keep in mind the fact that the light falling on dry sand passes through the air, and the light falling on the wet sand, through water.

Pour sand into a one-time paper plate. Pour from the edge of a plate some water. Noting the brightness of different sections of the sand in a plate, make a conclusion, in which sand scattering is larger: in dry (in which the grains are surrounded by air) or in wet (the sand is surrounded by water). You can try to experience other liquids, such as vegetable oil.

Didactic material

Spread of light

As we know, one of the types of heat transfer is radiation. When radiation, energy transmission from one body can be carried out even in vacuo. There are several varieties of emissions, one of them is visible light.

Lighted bodies gradually heat. So, light is indeed radiation.

Light phenomena are studied by a section of physics, which is called optics. The word "optics" in Greek means "visible", because the light is a visible type of radiation.

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

Body emitting light is called light sources - natural or artificial.

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

In any light source, energy is spent at radiation.

The sun radiates light due to energy from nuclear reactions occurring in its depths.

The kerosene lamp transforms the energy highlighted during kerosene combustion.

Reflection of light

A person sees a light source when the beam coming from this source enters the eye. If the body is not a source, then the eye can perceive the rays from a source reflected by this body, that is, falling on the surface of this body and have changed the direction of further distribution. The body reflecting the rays becomes a source of reflected light.

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

When we hear this word "reflection", first of all, we remember the mirror. Flat mirrors are most often used in everyday life. With the help of a flat mirror, you can carry out simple experience in order to establish the law by reflection of light. Illuminator to deliver on the table sheet of paper so that a thin beam of light lying in the plane of the table. In this case, the light beam will slide over the surface of a sheet of paper, and we will be able to see.

Set vertically on the path of the fine light beam. Flat mirror. A beam of light will affect him. You can make sure that the reflected bundle, like falling on the mirror, slides on paper in the plane of the table. We note a pencil on a sheet of paper The relative position of both light beams and mirrors. As a result, we obtain the scheme of the experiment. The yolat between the incident beam and perpendicular, restored to the reflective surface at the fall point, in the optics is called an angle of incidence. The angle between the perpendicular and the reflected beam - is the angle of reflection. The results of experience are:

1. The incident beam, reflected ray and perpendicular to the reflective surface, restored at the fall point, lie in the same plane.
2. The angle of the fall is equal to the angle of reflection. These two outputs are the law of reflection.

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

Consider an image of a point source in a flat mirror. To carry out this random multiple beams from the source, construct the corresponding reflected beams and then continue finish building the reflected beams for the plane mirrors. All continuations of the rays will cross over the plane of the mirror at one point: this point is the image of the source.

Since the rays themselves are converged in the image, but only their continuation, in fact there is no image at this point: we just think that rays come from this point. This image is called imaginary.

Refraction of light

When the light reaches the section of two media, part of it is reflected, the other part passes through the border, refraarting, that is, changing the direction of further distribution.

The coin immersed in the water seems to us more large compared to when it simply lies on the table. A pencil or a spoon placed in a glass with water, see us forced: a part in the water seems to be raised and slightly enlarged. These and many other optical phenomena are explained by the refraction of light.

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

The speed of light propagation in one or another medium characterizes the optical density of this medium: the higher the speed of light in this medium, the less its optical density.

How will the refractive angle change when moving light from air to water and when moving from water to the air? Experiments show that when moving from air to the water, the refractive angle turns out to be less than the angle of falling. Conversely: When moving from water to the air, the refractive angle is more than the angle of fall.

From the experiments on the refraction of the light, two facts became obvious: 1. The incident beam, refracted ray and perpendicular to the border of the section of two environments, restored at the point of the fall, lie in the same plane.

1. When moving from an optically more dense medium into an optically less dense refractive angle of more angle of fall.When moving from an optically less dense medium into an optically, a more dense refractive angle is less than an angle of falling.

An interesting phenomenon can be observed if gradually increase the angle of the fall when moving light into an optically less dense medium. The refractive angle in this case is known, more than the angle of falling, and, with an increase in the angle of falling, the refractive angle will also increase. With some value of the angle of incidence, the refractive angle will be equal to 90to.

We will gradually increase the angle of falling when moving light into an optically less dense environment. With increasing angle of fall, the refractive angle will also increase. When the refractive angle becomes equal to ninety degrees, the refracted beam does not switch to the second medium from the first, but slides in the plane of the boundaries of the sections of these two environments.

Such a phenomenon is called a complete internal reflection, and the angle of the fall at which it occurs - the limit angle of complete internal reflection.

The phenomenon of complete internal reflection is widely used in the technique. On this phenomenon, the use of flexible optical fibers, according to which light rays pass, repeatedly reflected from the walls.

The light does not go beyond the fiber due to the complete internal reflection. A simpler optical device in which a complete internal reflection is used is a revolving prism: it turns over the image by changing the rays included in it.

Image in lenses

The lens whose thickness is made compared with the radii of spheres, forming the surface of this lens, are called thin. In the future, we will consider only subtle lenses. In optical schemes, thin lenses are depicted in the form of segments with arrows at the ends. Depending on the direction of the arrows, the diagrams are distinguished by collecting and scattering lenses.

Consider how the beams parallel to the main optical axis passes through the lenses. Passing through

gathering lens, rays are collected at one point. Having passed through the scattering lens, the rays diverge in different directions in such a way that all their continued convergence at one point lying in front of the lens.

The point in which the rays are collected after refraction in the collecting lens, parallel to the main optical axis, is called the main focus of lenses-f.

In the scattering lense rays, parallel to its main optical axis, dissipate. The point in which the continued refracted rays are assembled, lies in front of the lens and is called the main focus of the scattering lenses.

The focus of the scattering lenses is obtained at the intersection of not the rays themselves, but their continuations, therefore it is imaginary, unlike collecting, who has a valid focus.

Lenses have two main focus. Both of them lie at equal distances from the optical center of the lens on its main optical axis.

The distance from the optical center of the lens to focus is customary called the focal length of the lenses. The stronger the lens changes the direction of the rays, the less it turns out its focal length. Therefore, the optical power of the lenses is inversely proportional to its focal length.

Optical force, as a rule, denote the letter "DE", and is measured in diopters. For example, writing down the recipe for points, indicate how many diopters should be the optical power of the right and left lenses.

diopteria (DPTR) is the optical force of the lens, the focal length of which is 1M. Since in collecting lenses, the focuses are valid, and in scattering - imaginary, then the optical force of collecting lenses of the positive value, and the optical force of the scattering lenses - negative

Who established the law of reflection of light?

For the XVI century, optics were ultra-modern science. Of glass ballfilled with water used as a focusing lens, a magnifying glass has occurred, and from it a microscope and a pickle tube. The largest Netherlands in those days of the Netherlands needed good pick-up pipes to look at the dangerous coast or in time to get away from the enemy. Optics ensured the success and reliability of navigation. Therefore, it was in the Netherlands that many scientists dealt with it. Hollandets Willebrord, Smell Wang Royen, who called himself Snallulius (1580 - 1626), watched (which, however, saw many to him), as a thin light beam reflected in the mirror. He simply measured the angle of the fall and the reflection angle of the beam (which no one did not do it) and established the law: the angle of the fall is equal to the reflection angle.

A source. Mirror world. Guild V. - M.: Mir, 1982. p. 24.

Why are diamonds appreciate so high?

Obviously, man especially appreciates everything that does not give in or difficult to change. Including precious metals and stones. The ancient Greeks called the Almaz "Adamas" - irresistible than they expressed their special attitude towards this stone. Of course, non-screwed stones (diamonds also did not granted) the most obvious properties were hardness and shine.

Diamonds are distinguished by a high refractive index; 2.41 - for red and 2.47 - for purple (for comparison, it is sufficient to say that the refractive index of water is 1.33, and the glass depending on the grade - from 1.5 to 1.75).

White light is composed of spectrum colors. And when its beam is refracted, each of the components of color rays deviates in different ways, it seems to be split into the colors of the rainbow. That is why there is a "game of flowers" in diamond.

The ancient Greeks undoubtedly admired and this. Not only is the stone is exceptional in shine and hardness, it also has the form of one of the "perfect" bodies of Plato!

Experiments

Optics experience №1

Explain the darkening of the tree bar after its wetting.

Equipment: Vessel with water, wooden bar.

Explain the fluctuation of the shadow of the stationary object when the light passes through the air over the burning candles.Equipment: tripod, ball on the thread, candle, screen, projector.

At the blades of the fan, turn the colored pieces of paper and follow how the colors are accumulated at different rotation modes. Explain the observed phenomenon.

Experience number2

According to the interference of light.

Simple demonstration of light absorption with aqueous solution of dye

It requires only a school illuminator, a glass with water and a white screen for its preparation. Dyes can be the most diverse, including fluorescents.

Students with great interest are observed a change in the color of the white light beam as it is propagated in the dye. Unexpected for them is the color of the beam out of the solution. Since the light focused on the illuminator lens, the stain color on the screen is determined by the distance between the glass with the liquid and the screen.

Simple experiments with lenses. (Experience number 3)

What happens to the image obtained using a lens if part of the lens crashed and the image is obtained using the remaining part of it?

Answer. The image will turn out in the same place where it was obtained using a whole lens, but its illumination will be less, because A smaller part of the rays that came out of the subject will reach its image.

Put the table illuminated by the sun (or a powerful lamp) a small brilliant object, for example, a ball from the bearing, or a bolt from the computer and look at it through the tiny hole in the foil sheet. Multicolored rings, or ovals, will be perfectly visible. What kind of phenomenon will be observed? Answer. Diffraction.

Simple experiments with colored glasses. (Experience number 4)

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

(ATTENTION! Be careful about the edge of the fragments you can wrap!)

Through what glass it is necessary to watch to see the evaluation "excellent"?

Answer. It is necessary to look through the green glass. At the same time, the inscription will be visible black on a green background of the paper, as the red light of the inscription "excellent" is not skipped with green glass. When viewed through the Red Glass, the red inscription will not be visible on a red paper background.

Experience number 5: Observation of the dispersion phenomenon

It is known that when skipping a narrow beam of white light through a glass prism on the screen installed in prisms, a rainbow strip can be observed, which is called a dispersion (or prismatic) spectrum. This spectrum is observed and then when the light source, the prism and the screen are placed in a closed vessel from which the air is rejected.

The results of the last experiment show that there is a dependence of the absolute refractive index of glass from the frequency of light waves. This phenomenon is observed in many substances and is called a dispersion of light. There are various experiments for illustration of a light dispersion phenomenon. The figure shows one of the options for its conduct.

The dispersion phenomenon of light was open to Newton and is considered one of its most important discoveries. At the tombstone monument, furnished in 1731, depicts shapes of young men holding the emblems of the most important discoveries of Newton. In the hands of one of the young men - Prism, and in the inscriptions on the monument there are such words: "He explored the difference in light rays and manifested various properties Flowers, which no one had previously suspected. "

Experience number 6: Does the mirror have a memory?

How to put a flat mirror on a drawn rectangle so that it turns out an image: triangle, quadrangle, pentagon.Equipment: Flat mirror, sheet of paper with squares drawn on it.

Questions

The transparent plexiglass becomes matte if his surface is lost by sandpaper. This glass becomes transparent again if it is lost ....Than?

On the scale of the lens diaphragm, numbers equal to the ratio of the focal length to the hole diameter are applied: 2; 2.8; 4.5; five; 5.8, etc. How will the shooting time change if the diaphragm is transferred to greater division of the scale?

Answer. Than more Number The diaphragmation designated on the scale, the lighting the image is less, and the excerpt required when photographing is more.

Most often, the lenses of cameras consist of several lenses. The light passing through the lens is partially reflected from the lenses surfaces. What defects does it lead to when shooting?Answer

When shooting snow plains and water surfaces in sunny days It is recommended to use the solar blend, which is a shredded inside the cylindrical or conical tube worn on
lens. What is the purpose of Blend?Answer

So that the light is not reflected inside the lens, the thinnest transparent film of the order of ten thousand millimeters is applied to the surface of the lenses. Such lenses are called enlightened. What physical phenomenon is based on the enlightenment of the lens? Explain why lenses do not reflect light.Answer.

Question for forum

Why black velvet seems much darker than black silk

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

Blitz

1. What are the names of the glasses without a student? (Pensne)

2. What gives an eagle during hunting? (Shadow.)

3. What is the famous artist Quenji? (Skill to portray air and lunar light transparency)

4. What are the lamps illuminating the scene? (Sofits)

5. Gemstone blue or greenish color? (Turquoise)

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

Blitz

1. What does not hide in the chest? (A ray of light)

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

3. What is more: cloud or shadow from her? (The cloud drops the complete shadow cone, the height of which due to the significant sizes of the cloud is great. Therefore, the shadow of the clouds differs little in size from the cloud itself)

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

5. Viden the edge, and you will not come. What is it? (Horizon)

Optical illusions.

Do not you think that black and white stripes move in opposite directions? If you tilt your head - then right, then left - the direction of rotation is also changing.

Infinite staircase leading up.

Sun and eye

do not be like the Sun eye,

I could not see it ... V.Gothe

Comparison of the eye and the sun is also old as the human himself. The source of such a comparison is not science. And in our time, next to science, simultaneously with the picture of the phenomena, disclosed and explained by the new natural science, continues to extend the world of the ideas of a child and primitive man and intentionally or unintentionally, imitating the world of poets. It is sometimes worth looking into this world as one of the possible sources of scientific hypotheses. He is amazing and fabricated; In this world, bridge-connections are boldly between the phenomena of nature, which other times of science still does not suspect. In some cases, these connections are guessed true, sometimes they are fundamentally erroneous and just ridiculous, but they always deserve attention, since these errors often help to understand the truth. Therefore, to the question of the connection of the eyes and the Sun instructively, first from the point of view of children's, primitive and poetic ideas.

Playing "in hide and seek", the child very often decides to hide the most unexpected way: he grieves his eyes or closes them with his hands, being sure that no one will see him; For him, vision is identified with light.

It is even more amazing, however, the preservation of the same instinctive mixing of vision and light in adults. Photographers, i.e. people are somewhat sophisticated in practical optics, often catch themselves on the fact that they close their eyes when, when charging or manifesting records, you need to carefully monitor the light to penetrate into the dark room.

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

Without noticing it, people say: "The eyes spranched", "the sun looked out," "stars are watching."

At poets, the transfer of visual representations on the luminaries and, on the contrary, attributing the eyes of the properties of light sources is the most common, one can say, a mandatory reception:

Night stars

As accusing eyes

It's mockingly look after him.

His eyes shine.

A.S. Pushkin.

With you on the stars we looked,

They are on us. Fet.

How does fish sees you?

Because of the refraction of the light, the fisherman sees the fish is not where it is in fact.

Folk signs

Most people remembering their school years, I am confident that physics is a very boring item. The course includes many tasks and formulas that will not use anyone in subsequent life. On the one hand, these statements are true, but, like any subject, physics has the other side of the medal. Only her not everyone opens for himself.

A lot depends on the teacher

It is possible that our education system is to blame for this, and maybe the whole thing in a teacher who thinks only that it is necessary to read the material approved above, and does not seek to interest his students. It is most often to blame for him. However, if children are lucky, and the lesson they will lead the teacher who himself loves his subject, he will not only be interested in students, but also will help them discover something new for themselves. As a result, will lead to the fact that the children will be happy to attend such classes. Of course, formulas are an integral part of this training subject, it is not going anywhere. But there are positive moments. Of particular interest among schoolchildren cause experiments. Here we will talk about it in more detail. We will look at some entertaining experiences in physics that you can spend along with your child. It should be interesting not only to him, but also you. It is likely that with the help of such classes you will give your choice of genuine interest in study, and the favorite subject will become "boring" physics for him. It is completely easy to carry out, this will require quite a few attributes, most importantly, to be desire. And, perhaps, then you can replace your child school teacher.

Consider some interesting experiences in physics for small, because you need to start with small.

Paper fish

To carry out this experiment, we need to cut out of thick paper (you can cardboard) a small fish whose length should be 30-50 mm. We do in the middle of a round hole with a diameter of about 10-15 mm. Next, from the side of the tail we cut the narrow channel (width 3-4 mm) to the round hole. After that, we pour water into the pelvis and gently put our fish in such a way that one plane lay on the water, and the second - remained dry. Now it is necessary to drop the oil into the round hole (you can use the oil from the sewing machine or bicycle). Oil, trying to break through the surface of the water, flows along the cutting channel, and the fish under the action of the resulting back oil floats forward.

Elephant and Moskka

We will continue to conduct entertaining experiences in physics with your child. We suggest you to acquaint the baby with the concept of the lever and with how it helps to facilitate the work of a person. For example, tell us that with it easily you can easily lift a heavy cabinet or sofa. And for clarity, show elementary experience in physics with the use of the lever. To do this, we need a ruler, pencil and a couple of small toys, but necessarily different weight (That is why we called this experience "Elephant and Pug"). Krepim is an elephant and a pug to different ends of the line with a plasticine, or a regular thread (just tie toys). Now, if we put a line of the middle part to the pencil, it will pull, of course, an elephant, because it is heavier. But if you shift a pencil toward the elephant, then the Pump will easily turn it out. This is the principle of the lever. The line (lever) rests on the pencil - this place is a point of support. Next, the child should be said that this principle is used everywhere, it is based on the work of the crane, swing and even scissors.

Home experience in physics with inertia

We will need a bank with water and economic grid. It will not be secret for anyone that if you turn over the open bank, the water will fall out of it. Let's try? Of course, it is better to go outside for this. We put the jar into the grid and begin to smoothly rock it, gradually increasing the amplitude, and as a result we make a full turn - one, second, third and so on. Water is not poured. Interesting? And now let's make the water pour out up. To do this, take a tin jar and make a hole in the bottom. We put on the grid, fill with water and start rotating. From the hole beats a jet. When the bank is in the lower position, it does not surprise anyone, but when it takes off up, then the fountain continues to beat in the same direction, and from the neck - not a drop. That's so. All this can explain the principle of inertia. When rotating the bank, it seeks to fly straight, and the grid does not allow it and causes the circle to describe it. Water also seeks to fly on the inertia, and in the case when we made a hole in the bottom, she does not prevent anything and move straight.

Boxes with surprise

Now consider experiments on physics with displacement you need to put a matchbox on the edge of the table and slowly move it. At that moment, when he passes his middle mark, there will be a drop. That is, the mass put forward by the edge of the table tops will exceed the weight of the remaining, and the boxes of the belch. Now we will resize the center of mass, for example, we set inside (as closer to the edge) metal nut. It remains to place the boxes so that the small part of it remains on the table, and the big hung in the air. Falls will not happen. The essence of this experiment consists in the fact that the whole mass is above the point of the support. This principle is also used everywhere. It is thanks to him in a sustainable position there are furniture, monuments, transport, and much more. By the way, the children's toy Vanka-stand is also built on the principle of displacement center of the mass.

So, continue to consider interesting experiences in physics, but we turn to the next stage - for schoolchildren of sixth grades.

Water carousel

We will need an empty cans, hammer, nail, rope. We pierce with the help of a nail and hammer in the side wall at the bottom of the hole. Further, without pulling the nail out of the hole, flexing him aside. It is necessary that the hole turns out oblique. We repeat the procedure from the second side of the bank - you need to do so that the holes are opposite each other, but nails were bent in different directions. In the upper part of the vessel there are two more holes, they produce the ends of the rope or thick thread. Let the container and fill it with water. From the lower holes will begin to beat two oblique fountains, and the bank will start rotating in the opposite direction. In this principle, we work space rockets - the flame from the engine nozzles beats in one direction, and the rocket flies to another.

Field Experiments - Grade 7

We will conduct an experiment with the density of the masses and learn how to make an egg to swim. Experiments on physics with various densities are best carried out on the example of fresh and salty water. Take the bank filled hot water. We lower the egg into it, and it will immediately drown. Next, we embarked in the water to the cook salt and stir. The egg begins to pop up, and the more salt, the higher it will rise. This is explained by salty water It has a higher density than fresh. So, everyone knows that in the Dead Sea (its water is the most salty) almost impossible to drown. As you can see, experiences in physics can significantly increase the horizons of your child.

and plastic bottle

Schoolchildren of seventh classes start learning atmosphere pressure And his impact on the items around us. To reveal this topic deeper, it is better to carry out the relevant experiments on physics. Atmospheric pressure affects us, although it remains invisible. We give an example with a balloon. Each of us can inflate it. Then we put it in plastic bottle, the edges of the row on the neck and fix. Thus, the air can only come in a ball, and the bottle will become a hermetically vessel. Now let's try to inflate the ball. We will not work out, as the atmospheric pressure in the bottle will not allow us to do this. When we blow, the ball begins to outweigh the air in the vessel. And since we have a bottle of tightness, then he has nowhere to go, and he begins to shrink, thereby becoming much more dense air in a bowl. Accordingly, the system is aligned, and it is impossible to inflate the ball. Now make a hole in the bottom and try to inflate the ball. In this case, no resistance, displaced the air leaves the bottle - the atmospheric pressure is aligned.

Conclusion

As you can see, experiments on physics are not difficult and quite interesting. Try to interest your child - and studying for him will be completely different, he will be happy to attend classes, which will eventually affect his progress.

Broken pencil

Experiment with arrows

It will surprise not only children, but also adults!

With children, you can still hold a couple of believes. For example, take the same amount of water and pour into different glasses (for example, wide and low, and the second is narrow and high.) And then ask what water is more?
And you can also put the same amount of coins (or buttons) in two rows (one under one). Ask the same amount in two rows. Then, removing one coin from one row, the rest to spread so that this series is the same as the top. And again ask the same now, etc. Try - Answers You will probably surprise you!

Ebbingauz Illusion (Ebbinghaus) or Titchener Circles - The optical illusion of the perception of relative sizes. The most famous version of this illusion is that two circles identical in size are placed nearby, and around one of them there are circles. big size, while the other is surrounded by small circles; At the same time, the first circle seems less than the second.

Two orange circles have exactly the same dimensions; However, the left circle seems less

Illusion of Muller Lyer

The illusion is that the segment framed by "episodes" seems shorter segment framed by the "tailing" arrows. The illusion was first described by the German psychiatrist Franz Muller Lyer in 1889

Or even here, for example, optical deception - first you see black, then white

Even more optical illusions

And at the end toy-illusion - Taumatridge.

With a quick rotation of a small piece of paper with two drawings deposited with of different sideThey are perceived as one. Such a toy can be done by yourself, having drawn or sticking the appropriate images (several common thaumatropes - flowers and a vase, a bird and a cage, a beetle and a bank) on a sufficiently thick paper and on the sides to attach ropes to twist. Or even easier - to attach to a wand, like a lollipop, and quickly rotate it between the palms.

And a couple of pictures. What do you see them?

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