Optical experiments for children. Experiments in optics experiments and experiments in physics on the topic. and a plastic bottle

Introduction

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

Physics experiments introduce students to the diverse applications of the laws of physics in a fun way. Experiments can be used in lessons to attract students’ attention to the phenomenon being studied, when repeating and consolidating educational material, and at physical evenings. Entertaining experiences deepen and expand students' knowledge, promote the development of logical thinking, and instill interest in the subject.

This work describes 10 entertaining experiments, 5 demonstration experiments using school equipment. The authors of the works are students of the 10th grade of Municipal Educational Institution Secondary School No. 1 in the village of Zabaikalsk, Transbaikal Territory - Chuguevsky Artyom, Lavrentyev Arkady, Chipizubov Dmitry. The guys independently carried out these experiments, summarized the results and presented them in the form of this work.

The role of experiment in the science of physics

The fact that physics is a young science
It’s impossible to say for sure here.
And in ancient times, learning science,
We always strived to comprehend it.

The purpose of teaching physics is specific,
Be able to apply all knowledge in practice.
And it’s important to remember – the role of experiment
Must stand in the first place.

Be able to plan an experiment and carry it out.
Analyze and bring to life.
Build a model, put forward a hypothesis,
Striving to reach new heights

The laws of physics are based on facts established experimentally. Moreover, the interpretation of the same facts often changes in the course of the historical development of physics. Facts accumulate through observation. But you can’t limit yourself to them only. This is only the first step towards knowledge. Next comes the experiment, the development of concepts that allow for qualitative characteristics. To draw from observations general conclusions, to find out the causes of the phenomena, it is necessary to establish quantitative relationships between quantities. If such a dependence is obtained, then a physical law has been found. If a physical law is found, then there is no need to experiment in each individual case; it is enough to perform the appropriate calculations. By experimentally studying quantitative relationships between quantities, patterns can be identified. Based on these laws, 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 experiments, discussion of the features of its setting and the observed results.

Entertaining experiments in physics

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

Experience name
Equipment and materials required for the experiment
Stages of the experiment
Explanation of experience

Experiment No. 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 five levels above each other. However, it will be more convenient for us to take not a glass, but a narrow glass that widens towards the top.

Pour salted tinted water into the bottom of the glass.
Roll up a “Funtik” from paper and bend its end at a right angle; cut off the 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 onto the salt water.
When the height of the layer of red wine is equal to the height of the layer of colored water, stop pouring the wine.
From the second cone, pour sunflower oil into a glass in the same way.
From the third horn, pour a layer of colored alcohol.

Picture 1

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

Explanation of experience

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

Experience No. 2 Amazing candlestick

Equipment and materials: candle, nail, 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

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

Explanation of experience

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

That’s the point,” you will answer, “that the candle is getting shorter every minute.” And if it’s shorter, it means it’s easier. If it’s easier, it means it will float up.

And, true, the candle will float up little by little, and the water-cooled paraffin 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, makes the candle lighter, which is why our candle will burn out to the end.

Experiment No. 3 Candle by bottle

Equipment and materials: candle, bottle, matches

Stages of the experiment

Place a lit candle behind the bottle, and stand so that your face is 20-30 cm away from the bottle.
Now you just need to blow and the candle will go out, as if there were 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 stream 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 candle flame stands.

Experiment No. 4 Spinning snake

Equipment and materials: thick paper, candle, scissors.

Stages of the experiment

Cut a spiral out of thick paper, stretch it a little and place it on the end of a curved wire.
Hold this spiral above the candle in the rising air flow, the snake will rotate.

Explanation of experience

The snake rotates because air expands under the influence of heat and warm energy is converted into movement.

Figure 4

Experiment No. 5 Eruption of Vesuvius

Equipment and materials: glass vessel, vial, stopper, alcohol ink, water.

Stages of the experiment

Place a bottle of alcohol ink in a wide glass vessel filled with water.
There should be a small hole in the bottle cap.

Figure 5

Explanation of experience

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

Experiment No. 6 Fifteen matches on one

Equipment and materials: 15 matches.

Stages of the experiment

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

Explanation of experience

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

Figure 6

Experiment No. 7 Pot stand

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

Stages of the experiment

Place three forks in a ring.
To put on this design plate.
Place a pan of water on the 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

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

Stages of the experiment

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

Heat the knitting needle and stick it with their heads into the candle. This will be the axis of our engine.
Place a candle with a knitting needle on the edges of two glasses and balance.
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 disrupted, the other end of the candle will tighten 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 go down, drop a drop, it will become lighter, and our motor will start working with all its might; gradually the candle's vibrations 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

Carefully cut the orange in half, peel so that the whole skin comes off.
Poke two holes side by side in the bottom of this cup and place 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.
Lower the orange cup into the vessel to one third of the height.
Pour red wine or colored alcohol into the orange peel. It will pass through the hole until the wine level reaches the bottom of the cup.
Then pour water almost to the edge. You can see how the stream of wine rises through one of the holes to the water level, 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.

Experiment No. 10 Singing glass

Equipment and materials: thin glass, water.

Stages of the experiment

Fill a glass with water and wipe the edges of the glass.
Rub a moistened finger anywhere on the glass and she will start singing.

Figure 11

Demonstration experiments

1. Diffusion of liquids and gases

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

Demonstration experiment “Observation of diffusion”

Equipment and materials: cotton wool, ammonia, phenolphthalein, installation for diffusion observation.

Stages of the experiment

Let's take two pieces of cotton wool.
We moisten one piece of cotton wool with phenolphthalein, the other with ammonia.
Let's bring the branches into contact.
The fleeces are observed to turn pink due to the phenomenon of diffusion.

Figure 12

Figure 13

Figure 14

The phenomenon of diffusion can be observed using a special installation

Pour ammonia into one of the flasks.
Moisten a piece of cotton wool with phenolphthalein and place it on top of the flask.
After some time, 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 occurs.

Figure 16

To demonstrate this experiment, let’s take two identical glasses. Pour cold water into one glass, hot water into the other. Let's add copper sulfate to the glasses and observe that copper sulfate 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 us take a number of vessels of various shapes, connected at the bottom by tubes.

Figure 19

Figure 20

Let us pour liquid into one of them: we will immediately find that the liquid will flow through the tubes into the remaining vessels and 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 surface of the level 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 the liquid behind the piston under the influence of atmospheric pressure.

To demonstrate the uniform transfer of pressure exerted on a liquid in a closed vessel, it is necessary to use a piston to draw water into the vessel and place the ball tightly on the nozzle. By pushing the piston into the vessel, demonstrate the flow of liquid from the holes in the ball, paying attention to the uniform flow of liquid in all directions.

Introduction

1.Literature review

1.1. 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 experimental methods

2.2. Experimental results

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

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

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

2.3. Discussion of experimental results

List of used literature

Introduction

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

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

Literature review

1.1 History of the development of geometric optics.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

FILM FRAGMENT

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

But what will this give you? - asked Watson.

I don’t know yet, was the answer.

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

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

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

And what follows from this? - Watson was perplexed.

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

The episode was repeated. Sherlock Holmes was thoughtful.

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

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

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

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

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

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

But the cyclist was moving,” Sherlock Holmes clarified.

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

Russian light

In 1876 in London at an exhibition of precision physical instrumentsditch Russian inventor Pavel Nikolaevich Ya blockkov demonstrated to visitors an extraordinary electrically a candle. Similar in shape to regular stearic, uh that candle burned with a blindingly bright light. In the same year, “Yablochkov candles” appeared on the streets of Paris. Placed in white matte balls, they gave a bright, pleasant light. INfor a short time the wonderful candle of the Russian inventorsfought to universal acclaim. "Yablochkov's candles" illuminated the best hotels, streets and parks of the largest cities in Europe, Accustomed to the dim light of candles and kerosene lamps, people of the last century admired the “Yablochkov candles.” New the light was called “Russian light”, “northern light”. Newspapers forWestern European countries wrote: “The light comes to us from the north - from Russia”, “Russia is the birthplace of light”.

Most people, recalling their school years, are sure that physics is a very boring subject. The course includes many problems 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 also has another side to 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 teach the material approved from above and does not strive to interest his students. Most often it is he who is to blame. However, if the children are lucky and the lesson is taught by a teacher who loves his subject, he will not only be able to interest the students, but will also help them discover something new. As a result, children will begin to enjoy attending such classes. Of course, formulas are an integral part of this academic subject; there is no escape from it. But there are also positive aspects. Experiments are of particular interest to schoolchildren. This is what we will talk about in more detail. We'll look at some fun physics experiments you can do with your child. This 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’s not at all difficult to carry out, it will require very few attributes, the main thing is that there is a desire. And perhaps then you will be able to replace your child’s school teacher.

Let's look at some interesting experiments in physics for 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 (can be cardboard), the length of which should be 30-50 mm. We make a round hole in the middle with a diameter of approximately 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 drop some oil into the round hole (you can use an oil can from a sewing machine or bicycle). The oil, trying to spread over the surface of the water, will flow through the cut channel, and the fish will swim forward under the influence of the oil flowing back.

Elephant and Moska

Let's continue to conduct entertaining experiments in physics with our child. We invite you to introduce your child to the concept of a lever and how it helps make a person’s work easier. For example, tell us that it can be used to easily lift a heavy cabinet or sofa. And for clarity, show a basic experiment in physics using a lever. For this we will 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 attach our Elephant and Pug to different ends of the ruler using plasticine or ordinary thread (we just tie the toys). Now, if you put the middle part of the ruler on a pencil, then, of course, the elephant will pull it, because it is heavier. But if you move the pencil towards the elephant, then Moska 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, swing, and even scissors.

Home experiment in physics with inertia

We will need a jar of water and a utility net. It will be no secret to anyone that if you turn an open jar over, water will pour out of it. Let's try? Of course, it’s better to go outside for this. We put the can in the net and begin to swing it smoothly, gradually increasing the amplitude, and as a result we make a full revolution - one, two, three, and so on. Water does not pour out. Interesting? Now let's make the water pour out. To do this, take a tin can and make a hole in the bottom. We put it in the net, fill it with water and start rotating. A stream comes out of the hole. When the can is in the lower position, this does not surprise anyone, but when it flies up, the fountain continues to flow in the same direction, and not a drop comes out of the neck. That's it. All this can be explained by the principle of inertia. When rotating, the can tends to fly straight away, but the mesh does not let it go and forces it to describe circles. Water also tends to fly by inertia, and in the case when we have made a hole in the bottom, there is nothing stopping it from breaking out and moving in a straight line.

Box with a surprise

Now let's look at physics experiments with displacement. You need to put a matchbox on the edge of the table and slowly move it. The moment it passes its average mark, a fall will occur. That is, the mass of the part pushed over the edge of the table top will exceed the weight of the remaining part, and the box 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). All that remains is to place the box in such a way that a small part of it remains on the table, and a large part hangs in the air. There will be no fall. 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 Vanka-Vstanka is also built on the principle of shifting the center of mass.

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

Water carousel

We will need an empty tin can, a hammer, a nail, and a rope. We use a nail and a hammer to punch a hole in the side wall near the bottom. Next, without pulling the nail out of the hole, bend it to the side. It is necessary that the hole is 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 and thread the ends of a rope or thick thread into them. We hang the container and fill it with water. Two oblique fountains will begin to flow from the lower holes, and the jar will begin to rotate in the opposite direction. Space rockets work on this principle - the flame from the engine nozzles shoots in one direction, and the rocket flies in the other.

Experiments in physics - 7th grade

Let's conduct an experiment with mass density and find out how you can make an egg float. Physics experiments with different densities This is best done using fresh and salt water as an example. Take a jar filled with hot water. Drop an egg into it and it will immediately sink. Next, add table salt to the water and stir. The egg begins to float, and the more salt, the higher it will rise. This is explained by salty water has a higher density than fresh water. So, everyone knows that in the Dead Sea (its water is the saltiest) it is almost impossible to drown. As you can see, experiments in physics can significantly expand your child’s horizons.

and a plastic bottle

Seventh grade students begin to study atmospheric pressure and its effect on the objects around us. To explore this topic deeper, 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 cheat it. Then we will place it in a plastic bottle, put the edges on the neck and secure it. This way, air can only flow into the ball, and the bottle will become 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 ball begins to displace the air in the container. And since our bottle is sealed, it has nowhere to go, and it begins to shrink, thereby becoming much more denser than air in a ball. Accordingly, the system is leveled, and it is impossible to inflate the balloon. Now we’ll 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 - the atmospheric pressure is equalized.

Conclusion

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

LIGHT SCATTERING

Particles of matter that transmit light behave like tiny antennas. These "antennas" receive light electromagnetic waves, and transmit them in new directions. This process is called Rayleigh scattering after the English physicist Lord Rayleigh (John William Strett, 1842-1919).

Experience 1

Place a sheet of white paper on the table and a flashlight next to it so that the light source is located in the middle of the long side of the sheet of paper.
Fill two clear, clear plastic glasses with water. Using a marker, label the glasses with the letters A and B.
Add a drop of milk to glass B and stir
Place a 15x30cm sheet of white cardboard with the short ends together and fold it in half to form a hut. It will serve as your screen. Place the screen opposite the flashlight, with opposite side sheet of paper.

Darken the room, turn on the flashlight and notice the color of the light spot formed by the flashlight on the screen.
Place glass A in the center of a 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 light from the flashlight passing through the water; Look closely at the water and notice how the color of the water has changed.
Repeat the steps, replacing glass A with glass B.

As a result, the color of the light spot formed on the screen by a beam of light from a flashlight, in the path of which there is nothing but air, may be white or slightly yellowish. When a beam of light passes through clean water, the color of the spot on the screen does not change. The color of the water does not change either.
But after passing the beam through water to which milk has been added, the light spot on the screen appears yellow or even orange, and the water becomes bluish.

Why?
Light, like electromagnetic radiation In general, it has both wave and corpuscular properties. The propagation of light has a wave-like character, and its interaction with matter occurs as if the light radiation consists of individual particles. Light particles - quanta (aka photons) are clots of energy with different frequencies.

Photons have the properties of both particles and waves. Since photons undergo wave vibrations, the size of the photon is taken to be the wavelength of light of the corresponding frequency.
The flashlight is a source of white light. This is visible light, consisting of all possible shades of colors, i.e. radiation of different wavelengths - from red, with the longest wavelength, to blue and violet, with the shortest wavelengths in the visible range. When light vibrations of different wavelengths are mixed, the eye perceives them and the brain interprets this combination as white, i.e. lack of color. Light passes through pure water without acquiring any color.

But when light passes through water tinted with milk, we notice that the water has become bluish, and the light spot on the screen has turned yellow-orange. This occurred as a result of scattering (deviation) of part of the light waves. Scattering can be elastic (reflection), in which photons collide with particles and bounce off them, just like two billiard balls bounce off each other. A photon undergoes the greatest scattering when it collides with a particle approximately the same size as itself.

Small particles of milk in water best scatter radiation of short wavelengths - blue and violet. Thus, when white light passes through water tinted with milk, the sensation of a pale blue color arises due to the scattering of short wavelengths. After short wavelengths from the light beam are scattered by milk particles, the wavelengths that remain are mainly yellow and orange. They move on to the screen.

If the particle size is larger than the maximum wavelength of visible light, the scattered light will consist of all wavelengths; such light will be white.

Experience 2

How does scattering depend on particle concentration?
Repeat the experiment using different concentrations of milk in water, from 0 to 10 drops. Observe the changes in the colors of the water and the light transmitted by the water.

Experience 3

Does the scattering of light in a medium depend on the speed of light in this medium?
The speed of light depends on the density of the substance in which the light travels. The higher the density of the medium, the slower light propagates through it

Remember that the scattering of light in different substances can be compared by observing the brightness of those substances. Knowing that the speed of light in air is 3 x 108 m/s, and the speed of light in water is 2.23 x 108 m/s, we can compare, for example, the brightness of wet river sand with the brightness of dry sand. In this case, one must keep in mind the fact that light falling on dry sand passes through air, and light falling on wet sand passes through water.

Place sand in a disposable paper plate. Pour some water from the edge of the plate. Having noted the brightness of different parts of the sand in the plate, draw a conclusion in which sand the scattering is greater: dry (in which the sand grains are surrounded by air) or wet (the sand grains are surrounded by water). You can try other liquids, for example, vegetable oil.