Experiments in optics experiments and experiments in physics on the topic. Optical illusion

broken pencil

Arrow experiment

It will surprise not only children, but also adults!

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

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

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

Muller-Lyer illusion

The illusion is that the segment framed by the "points" seems to be shorter than the segment framed by the "tail" arrows. The illusion was first described by the German psychiatrist Franz Müller-Lyer in 1889.

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

More optical illusions

And in the end, a toy-illusion - Thaumatrope.

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

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

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

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There are very simple experiences that children remember for a lifetime. The guys may not fully understand why this is all happening, but when time passes and they find themselves in a lesson in physics or chemistry, a very clear example will surely pop up in their memory.

website collected 7 interesting experiments that children will remember. Everything you need for these experiments is at your fingertips.

refractory ball

It will take: 2 balls, candle, matches, water.

An experience: Inflate a balloon and hold it over a lighted candle to show the children that the balloon will burst from fire. Then pour plain tap water into the second ball, tie it up and bring it to the candle again. It turns out that with water the ball can easily withstand the flame of a candle.

Explanation: The water in the balloon absorbs the heat generated by the candle. Therefore, the ball itself will not burn and, therefore, will not burst.

Pencils

You will need: plastic bag, pencils, water.

An experience: Pour water halfway into a plastic bag. We pierce the bag through with a pencil in the place where it is filled with water.

Explanation: If you pierce a plastic bag and then pour water into it, it will pour out through the holes. But if you first fill the bag halfway with water and then pierce it with a sharp object so that the object remains stuck in the bag, then almost no water will flow out through these holes. This is due to the fact that when polyethylene breaks, its molecules are attracted closer to each other. In our case, the polyethylene is pulled around the pencils.

Non-popping ball

You will need: balloon, wooden skewer and some dishwashing liquid.

An experience: Lubricate the top and bottom with the product and pierce the ball, starting from the bottom.

Explanation: The secret of this trick is simple. In order to save the ball, you need to pierce it at the points of least tension, and they are located at the bottom and at the top of the ball.

Cauliflower

It will take: 4 cups of water, food coloring, cabbage leaves or white flowers.

An experience: Add food coloring of any color to each glass and put one leaf or flower into the water. Leave them overnight. In the morning you will see that they have turned into different colors.

Explanation: Plants absorb water and thus nourish their flowers and leaves. This is due to the capillary effect, in which the water itself tends to fill the thin tubes inside the plants. This is how flowers, grass, and large trees feed. By sucking in tinted water, they change their color.

floating egg

It will take: 2 eggs, 2 glasses of water, salt.

An experience: Gently place the egg in a glass of plain clean water. As expected, it will sink to the bottom (if not, the egg may be rotten and should not be returned to the refrigerator). Pour warm water into the second glass and stir 4-5 tablespoons of salt in it. For the purity of the experiment, you can wait until the water cools down. Then dip the second egg into the water. It will float near the surface.

Explanation: It's all about density. The average density of an egg is much greater than that of plain water, so the egg sinks down. And the density of the saline solution is higher, and therefore the egg rises.

crystal lollipops

Didactic material

Spread of light

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

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

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

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

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

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

In any light source, radiation consumes energy.

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

A kerosene lamp converts the energy released during the combustion of kerosene into light.

reflection of light

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

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

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

Let us place a flat mirror vertically in the path of a thin light beam. A beam of light will bounce off it. It can be verified that the reflected beam, like the one incident on the mirror, slides over the paper in the plane of the table. Mark with a pencil on a sheet of paper the relative position of both light beams and the mirror. As a result, we obtain a scheme of the experiment. The angle between the incident beam and the perpendicular restored to the reflecting surface at the point of incidence is usually called the angle of incidence in optics. The angle between the same perpendicular and the reflected beam is the angle of reflection. The results of the experience are:

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

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

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

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

Light refraction

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

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

Refraction of light is due to the fact that light travels at different speeds in different media.

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

How will the angle of refraction change when light passes from air to water and when it passes from water to air? Experiments show that when passing from air to water, the angle of refraction is smaller than the angle of incidence. And vice versa: when passing from water to air, the angle of refraction is greater than the angle of incidence.

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

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

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

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

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

The phenomenon of total internal reflection is widely used in technology. This phenomenon is based on the use of flexible optical fibers, through which light rays pass, repeatedly reflected from the walls.

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

Image in lenses

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

Let us consider how a beam of rays parallel to the main optical axis passes through the lenses. Coming through

converging lens, the rays are collected at one point. After passing through a diverging lens, the rays diverge in different directions in such a way that all their continuations converge at one point lying in front of the lens.

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

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

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

The lens has two main foci. 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 the focus is called the focal length of the lens. The more the lens changes the direction of the rays, the smaller its focal length is. Therefore, the optical power of a lens is inversely proportional to its focal length.

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

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

Who established the law of reflection of light?

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

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

Why are diamonds valued so highly?

Obviously, a person especially appreciates everything that does not lend itself or is difficult to change. Including precious metals and stones. The ancient Greeks called the diamond "adamas" - irresistible, which expressed their special attitude to this stone. Of course, in rough stones (diamonds were also not cut), the most obvious properties were hardness and brilliance.

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

White light is made up of the colors of the spectrum. And when its ray is refracted, each of the constituent colored rays is deflected differently, as if it splits into the colors of the rainbow. That is why there is a "play of colors" in a diamond.

The ancient Greeks were undoubtedly fascinated by this too. Not only is the stone exceptional in brilliance and hardness, it also has the shape of one of Plato's "perfect" solids!

Experiences

EXPERIENCE in optics No. 1

Explain the darkening of a block of wood after wetting it.

Equipment: vessel with water, wooden block.

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

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

EXPERIENCE #2

By the interference of light.

A simple demonstration of the absorption of light by an aqueous dye solution

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

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

Simple experiments with lenses. (EXPERIMENT No. 3)

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

Answer . The image will be obtained in the same place where it was obtained with the help of a whole lens, but its illumination will be less, because. a smaller part of the rays coming out of the object will reach its image.

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

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

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

(Attention! be careful, you can get hurt on the edges of the fragments!)

Through which glass do you need to look to see the “excellent” rating?

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

EXPERIMENT #5: Observation of the phenomenon of dispersion

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

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

The phenomenon of light dispersion was discovered by Newton and is considered one of his most important discoveries. The tombstone erected in 1731 depicts the figures of young men holding the emblems of Newton's most important discoveries. In the hands of one of the young men there is a prism, and in the inscription on the monument there are the following words: "He investigated the difference of light rays and the various properties of colors manifested in this, which no one had suspected before."

EXPERIENCE #6: Does a mirror have memory?

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

QUESTIONS

Transparent plexiglass becomes opaque if its surface is rubbed with sandpaper. The same glass becomes transparent again when rubbed....How?

Numbers equal to the ratio of the focal length to the aperture diameter are marked on the lens aperture scale: 2; 2.8; 4.5; 5; 5.8, etc. How will the exposure time change if the aperture is moved to a larger division of the scale?

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

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

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

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

Question for forum

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

Why doesn't white light break down into its components when it passes through a window pane?Answer.

Blitz

1. What are glasses without temples called? (pince-nez)

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

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

4. What are the lamps that light up the stage called? (soffits)

5. Is the gem blue or greenish?(Turquoise)

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

Blitz

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

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

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

4. You follow her, she follows you, you follow her, she follows you. What it is? (Shadow)

5. The edge is visible, but you will not reach it. What is it? (horizon)

Optical illusions.

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

An endless staircase leading up.

sun and eye

do not be like the Sun of the eyes,

He couldn't see the sun... W. Goethe

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

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

Even more surprising, however, is the persistence of the same instinctive confusion of vision and light in adults. Photographers, that is, people who are somewhat experienced in practical optics, often catch themselves closing their eyes when, when loading or developing plates, care must be taken that light does not penetrate into a dark room.

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

Without noticing this, people say: "the eyes sparkled", "the sun came out", "the stars are watching."

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

Stars of the night

Like accusatory eyes

They look at him mockingly.

His eyes are shining.

A.S. Pushkin.

We looked at the stars with you

They are on us. Fet.

How do fish see you?

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

Folk omens

Most people, remembering their school years, are sure that physics is a very boring subject. The course includes many tasks and formulas that will not be useful to anyone in later life. On the one hand, these statements are true, but, like any subject, physics has the other side of the coin. But not everyone discovers it for themselves.

A lot depends on the teacher.

Perhaps our education system is to blame for this, or maybe it's all about the teacher, who thinks only about the need to reprimand the material approved from above, and does not seek to interest his students. Most of the time it's his fault. However, if the children are lucky, and the lesson will be taught by a teacher who loves his subject himself, then he will be able not only to interest the students, but also help them discover something new. As a result, it will lead to the fact that children will begin to attend such classes with pleasure. Of course, formulas are an integral part of this academic subject, there is no escape from this. But there are also positive aspects. Experiments are of particular interest to students. Here we will talk about this in more detail. We will look at some fun physics experiments that you can do with your child. It should be interesting not only to him, but also to you. It is likely that with the help of such activities you will instill in your child a genuine interest in learning, and "boring" physics will become his favorite subject. it is not difficult to carry out, this will require very few attributes, the main thing is that there is a desire. And, perhaps, then you can replace your child with a school teacher.

Consider some interesting experiments in physics for the little ones, because you need to start small.

paper fish

To conduct this experiment, we need to cut out a small fish from thick paper (you can use cardboard), the length of which should be 30-50 mm. We make a round hole in the middle with a diameter of about 10-15 mm. Next, from the side of the tail, we cut a narrow channel (width 3-4 mm) to a round hole. Then we pour water into the basin and carefully place our fish there so that one plane lies on the water, and the second remains dry. Now you need to drip oil into the round hole (you can use an oiler from a sewing machine or a bicycle). The oil, trying to spill over the surface of the water, will flow through the cut channel, and the fish, under the action of the oil flowing back, will swim forward.

Elephant and Pug

Let's continue to conduct entertaining experiments in physics with your child. We suggest that you introduce your baby to the concept of a lever and how it helps to facilitate a person’s work. For example, tell us that you can easily lift a heavy wardrobe or sofa with it. And for clarity, show an elementary experiment in physics using a lever. To do this, we need a ruler, a pencil and a couple of small toys, but always of different weights (that's why we called this experiment "Elephant and Pug"). We fasten our Elephant and Pug to different ends of the ruler using plasticine, or an ordinary thread (we just tie the toys). Now, if you put the ruler with the middle part on the pencil, then, of course, the elephant will pull, because it is heavier. But if you shift the pencil towards the elephant, then Pug will easily outweigh it. This is the principle of leverage. The ruler (lever) rests on the pencil - this place is the fulcrum. Next, the child should be told that this principle is used everywhere, it is the basis for the operation of a crane, a swing, and even scissors.

Home experience in physics with inertia

We will need a jar of water and a household net. It will not be a secret for anyone that if you turn an open jar over, the water will pour out of it. Let's try? Of course, for this it is better to go outside. We put the jar in the grid and begin to smoothly swing it, gradually increasing the amplitude, and as a result we make a full turn - one, two, three, and so on. Water does not pour out. Interesting? And now let's make the water pour up. To do this, take a tin can and make a hole in the bottom. We put it in the grid, fill it with water and begin to rotate. A stream shoots out of the hole. When the jar is in the lower position, this does not surprise anyone, but when it flies up, the fountain continues to beat in the same direction, and not a drop from the neck. That's it. All this can explain the principle of inertia. When the bank rotates, it tends to fly straight, but the grid does not let it go and makes it describe circles. Water also tends to fly by inertia, and in the case when we made a hole in the bottom, nothing prevents it from breaking out and moving in a straight line.

Box with a surprise

Now consider experiments in physics with displacement. You need to put a matchbox on the edge of the table and slowly move it. The moment it passes its middle mark, a fall will occur. That is, the mass of the part extended beyond the edge of the tabletop will exceed the weight of the remaining one, and the boxes will tip over. Now let's shift the center of mass, for example, put a metal nut inside (as close to the edge as possible). It remains to place the boxes in such a way that a small part of it remains on the table, and a large one hangs in the air. The fall will not happen. The essence of this experiment is that the entire mass is above the fulcrum. This principle is also used throughout. It is thanks to him that furniture, monuments, transport, and much more are in a stable position. By the way, the children's toy Roly-Vstanka is also built on the principle of shifting the center of mass.

So, let's continue to consider interesting experiments in physics, but let's move on to the next stage - for sixth grade students.

water carousel

We need an empty tin can, a hammer, a nail, a rope. We pierce a hole in the side wall at the very bottom with a nail and a hammer. Next, without pulling the nail out of the hole, bend it to the side. It is necessary that the hole be oblique. We repeat the procedure on the second side of the can - you need to make sure that the holes are opposite each other, but the nails are bent in different directions. We punch two more holes in the upper part of the vessel, we pass the ends of a rope or a thick thread through them. We hang the container and fill it with water. Two oblique fountains will start to beat from the lower holes, and the can will begin to rotate in the opposite direction. Space rockets work on this principle - the flame from the engine nozzles hits in one direction, and the rocket flies in the other.

Experiments in physics - Grade 7

Let's do an experiment with mass density and find out how you can make an egg float. Experiments in physics with different densities are best done on the example of fresh and salt water. Take a jar filled with hot water. We put an egg in it, and it immediately sinks. Next, add salt to the water and stir. The egg begins to float, and the more salt, the higher it will rise. This is because salt water has a higher density than fresh water. So, everyone knows that in the Dead Sea (its water is the most salty) it is almost impossible to drown. As you can see, experiments in physics can significantly increase the horizons of your child.

and a plastic bottle

Schoolchildren of the seventh grade begin to study atmospheric pressure and its effect on the objects around us. To reveal this topic more deeply, it is better to conduct appropriate experiments in physics. Atmospheric pressure affects us, although it remains invisible. Let's take an example with a balloon. Each of us can inflate it. Then we will put it in a plastic bottle, put the edges on the neck and fix it. Thus, air can only enter the ball, and the bottle becomes a sealed vessel. Now let's try to inflate the balloon. We will not succeed, since the atmospheric pressure in the bottle will not allow us to do this. When we blow, the balloon begins to displace the air in the vessel. And since our bottle is airtight, it has nowhere to go, and it begins to shrink, thereby becoming much denser than the air in the ball. Accordingly, the system is leveled, and it is impossible to inflate the balloon. Now we will make a hole in the bottom and try to inflate the balloon. In this case, there is no resistance, the displaced air leaves the bottle - atmospheric pressure equalizes.

Conclusion

As you can see, experiments in physics are not at all complicated and quite interesting. Try to interest your child - and studying for him will be completely different, he will begin to attend classes with pleasure, which will eventually affect his academic performance.

Introduction

Without a doubt, all our knowledge begins with experience.
(Kant Emmanuel. German philosopher 1724-1804)

Physical experiments in an entertaining way introduce students to the various applications of the laws of physics. Experiments can be used in the classroom to draw students' attention to the phenomenon being studied, when repeating and consolidating educational material, and at physical evenings. Entertaining experiments deepen and expand students' knowledge, contribute to the development of logical thinking, instill interest in the subject.

This paper describes 10 entertaining experiments, 5 demonstration experiments using school equipment. The authors of the works are students of the 10th grade of the MOU secondary school No. 1 of the village of Zabaikalsk, Zabaikalsky Krai - Chuguevsky Artyom, Lavrentiev Arkady, Chipizubov Dmitry. The guys independently did these experiments, summarized the results and presented them in the form of this work.

The role of experiment in the science of physics

That physics is a young science
Can't say for sure here.
And in ancient times knowing science,
Always strive to reach it.

The purpose of teaching physics is specific,
To be able to apply all knowledge in practice.
And it is important to remember - the role of the experiment
Must be in the first place.

Know how to plan and execute experiments.
Analyze and bring to life.
Build a model, put forward a hypothesis,
Strive to reach new heights

The laws of physics are based on facts established by experience. Moreover, the interpretation of the same facts often changes in the course of the historical development of physics. Facts accumulate as a result of observations. But at the same time, they cannot be limited only to them. This is only the first step towards knowledge. Next comes the experiment, the development of concepts that allow qualitative characteristics. In order to draw general conclusions from observations, to find out the causes of phenomena, it is necessary to establish quantitative relationships between quantities. If such a dependence is obtained, then a physical law is found. If a physical law is found, then there is no need to set up an experiment in each individual case, it is enough to perform the appropriate calculations. Having studied experimentally the quantitative relationships between the quantities, it is possible to identify patterns. Based on these regularities, a general theory of phenomena is developed.

Therefore, without experiment there can be no rational teaching of physics. The study of physics involves the widespread use of the experiment, the discussion of the features of its formulation and the observed results.

Entertaining experiments in physics

The description of the experiments was carried out using the following algorithm:

1. Name of experience
2. Instruments and materials necessary for the experiment
3. Stages of the experiment
4. Explanation of experience

Experience #1 Four floors

Equipment and materials: glass, paper, scissors, water, salt, red wine, sunflower oil, colored alcohol.

Stages of the experiment

Let's try to pour four different liquids into a glass so that they do not mix and stand one above the other in five floors. However, it will be more convenient for us to take not a glass, but a narrow glass expanding towards the top.

1. Pour salted tinted water into the bottom of a glass.
2. Roll out “Funtik” paper and bend its end at a right angle; cut off its tip. The hole in the Funtik should be the size of a pinhead. Pour red wine into this cone; a thin stream should flow out of it horizontally, break against the walls of the glass and flow down it into salt water.
   When the layer of red wine is equal in height to the height of the layer of tinted water, stop pouring the wine.
3. From the second cone, pour sunflower oil into a glass in the same way.
4. Pour a layer of colored alcohol from the third horn.

Picture 1

So we got four floors of liquids in one glass. All different colors and different densities.

Explanation of experience

The liquids in the groceries were arranged in the following order: tinted water, red wine, sunflower oil, tinted alcohol. The heaviest are at the bottom, the lightest are at the top. Salt water has the highest density, tinted alcohol has the smallest.

Experience #2 Amazing Candlestick

Devices and materials: a candle, a nail, a glass, matches, water.

Stages of the experiment

Isn't it an amazing candlestick - a glass of water? And this candlestick is not bad at all.

Figure 2

1. Weight the end of the candle with a nail.
2. Calculate the size of the nail so that the candle is completely immersed in water, only the wick and the very tip of the paraffin should protrude above the water.
3. Light the fuse.

Explanation of experience

Let me, they will tell you, because in a minute the candle will burn down to water and go out!

That's just the point, - you will answer, - that the candle is getting shorter every minute. And if it's shorter, it's easier. If it's easier, then it will float.

And, true, the candle will gradually float up, and the paraffin cooled by water at the edge of the candle will melt more slowly than the paraffin surrounding the wick. Therefore, a rather deep funnel is formed around the wick. This emptiness, in turn, lightens the candle, and that is why our candle will burn out to the end.

Experience No. 3 Candle behind a bottle

Equipment and materials: candle, bottle, matches

Stages of the experiment

1. Put a lit candle behind the bottle, and stand yourself so that your face is 20-30 cm away from the bottle.
2. It is worth now to blow, and the candle will go out, as if there is no barrier between you and the candle.

Figure 3

Explanation of experience

The candle goes out because the bottle is “flown around” with air: the jet of air is broken by the bottle into two streams; one flows around it on the right, and the other on the left; and they meet approximately where the flame of a candle stands.

Experience number 4 Spinning snake

Tools and materials: thick paper, candle, scissors.

Stages of the experiment

1. Cut a spiral out of thick paper, stretch it a little and put it on the end of the bent wire.
2. Holding this coil over the candle in an updraft of air will cause the snake to spin.

Explanation of experience

The snake rotates because there is an expansion of air under the action of heat and the transformation of warm energy into motion.

Figure 4

Experience No. 5 Eruption of Vesuvius

Devices and materials: glass vessel, vial, cork, alcohol ink, water.

Stages of the experiment

1. In a wide glass vessel filled with water, put a vial of alcohol ink.
2. There should be a small hole in the stopper of the vial.

Figure 5

Explanation of experience

Water has a higher density than alcohol; it will gradually enter the vial, displacing the mascara from there. Red, blue or black liquid will rise in a thin stream from the bubble upwards.

Experiment No. 6 Fifteen matches on one

Equipment and materials: 15 matches.

Stages of the experiment

1. Put one match on the table, and 14 matches across it so that their heads stick up and the ends touch the table.
2. How to lift the first match, holding it by one end, and with it all the other matches?

Explanation of experience

To do this, you only need to put one more, fifteenth match on top of all the matches, in the hollow between them.

Figure 6

Experience No. 7 Pot stand

Equipment and materials: a plate, 3 forks, a napkin ring, a saucepan.

Stages of the experiment

1. Put three forks in the ring.
2. Put a plate on this design.
3. Place a pot of water on a stand.

Figure 7

Figure 8

Explanation of experience

This experience is explained by the rule of leverage and stable equilibrium.

Figure 9

Experience No. 8 Paraffin motor

Devices and materials: a candle, a knitting needle, 2 glasses, 2 plates, matches.

Stages of the experiment

To make this motor, we don't need electricity or gasoline. We need only ... a candle for this.

1. Heat the needle and stick it with their heads into the candle. This will be the axis of our engine.
2. Place a candle with a knitting needle on the edges of two glasses and balance.
3. Light the candle at both ends.

Explanation of experience

A drop of paraffin will fall into one of the plates placed under the ends of the candle. The balance will be disturbed, the other end of the candle will pull and fall; at the same time, a few drops of paraffin will drain from it, and it will become lighter than the first end; it rises to the top, the first end will fall, drop a drop, it will become easier, and our motor will start to work with might and main; gradually fluctuations of the candle will increase more and more.

Figure 10

Experience No. 9 Free exchange of fluids

Equipment and materials: orange, glass, red wine or milk, water, 2 toothpicks.

Stages of the experiment

1. Carefully cut the orange in half, peel so that the skin is removed by a whole cup.
2. Poke two holes in the bottom of this cup side by side and put it in a glass. The diameter of the cup should be slightly larger than the diameter of the central part of the glass, then the cup will stay on the walls without falling to the bottom.
3. Lower the orange cup into the vessel one third of the height.
4. Pour red wine or colored alcohol into an orange peel. It will pass through the hole until the level of the wine reaches the bottom of the cup.
5. Then pour water almost to the brim. You can see how a stream of wine rises through one of the holes to the level of the water, while the heavier water passes through the other hole and begins to sink to the bottom of the glass. In a few moments the wine will be at the top and the water at the bottom.

Experience No. 10 Singing glass

Equipment and materials: a thin glass, water.

Stages of the experiment

1. Fill a glass with water and wipe the rim of the glass.
2. With a moistened finger, rub anywhere in the glass, she will sing.

Figure 11

Demonstration Experiments

1. Diffusion of liquids and gases

Diffusion (from Latin diflusio - spreading, spreading, scattering), the transfer of particles of different nature, due to the chaotic thermal motion of molecules (atoms). Distinguish between diffusion in liquids, gases and solids

Demonstration experiment "Observation of diffusion"

Devices and materials: cotton wool, ammonia, phenolphthalein, a device for observing diffusion.

Stages of the experiment

1. Take two pieces of cotton wool.
2. We moisten one piece of cotton wool with phenolphthalein, the other with ammonia.
3. Let's bring the branches together.
4. There is a pink staining of the fleece due to the phenomenon of diffusion.

Figure 12

Figure 13

Figure 14

The phenomenon of diffusion can be observed using a special installation

1. Pour ammonia into one of the cones.
2. Moisten a piece of cotton wool with phenolphthalein and put it on top in a flask.
3. After a while, we observe the coloring of the fleece. This experiment demonstrates the phenomenon of diffusion at a distance.

Figure 15

Let us prove that the phenomenon of diffusion depends on temperature. The higher the temperature, the faster diffusion proceeds.

Figure 16

To demonstrate this experiment, let's take two identical glasses. Pour cold water into one glass, hot water into the other. We add copper sulphate to glasses, we observe that copper sulphate dissolves faster in hot water, which proves the dependence of diffusion on temperature.

Figure 17

Figure 18

2. Communicating vessels

To demonstrate communicating vessels, let's take a number of vessels of various shapes, connected at the bottom by tubes.

Figure 19

Figure 20

We will pour liquid into one of them: we will immediately find that the liquid will flow through the tubes into the remaining vessels and will settle in all vessels at the same level.

The explanation for this experience is as follows. The pressure on the free surfaces of the liquid in the vessels is the same; it is equal to atmospheric pressure. Thus, all free surfaces belong to the same level surface and, therefore, must be in the same horizontal plane and the upper edge of the vessel itself: otherwise the kettle cannot be filled to the top.

Figure 21

3. Pascal's ball

Pascal's ball is a device designed to demonstrate the uniform transfer of pressure exerted on a liquid or gas in a closed vessel, as well as the rise of a liquid behind a piston under the influence of atmospheric pressure.

To demonstrate the uniform transmission of pressure produced on a liquid in a closed vessel, it is necessary, using a piston, to draw water into the vessel and tightly fit a ball onto the nozzle. By pushing the piston into the vessel, demonstrate the outflow of liquid from the holes in the ball, paying attention to the uniform outflow of liquid in all directions.