Optical experiments at home. Optical illusion. Optical illusions. The history of the development of geometric optics
LIGHT SCATTERING
Particles of a substance that transmits 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).
Test 1
Place a sheet of white paper on a table and a flashlight next to it so that the light source is in the middle of the long side of the sheet of paper.
Fill two colorless clear plastic glasses with water. Use a marker to mark the glasses with the letters A and B.
Add a drop of milk to glass B and stir
Fold a 15x30 cm sheet of white cardboard together with the short ends and fold it in half to form a hut. It will serve as a screen for you. Place the screen in front of the flashlight, on the opposite side of the 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 the sheet of paper, in front of the flashlight, and do the following: notice the color of the spot of light on the screen, which is formed as a result of the passage of light from the flashlight through the water; take a close look 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, can be white or slightly yellowish. When a beam of light passes through clear water, the color of the spot on the screen does not change. The color of the water also does not change.
But after passing the beam through water to which milk is added, the light spot on the screen appears yellow or even orange, and the water becomes bluish.
Why?
Light, like electromagnetic radiation in general, 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 bunches of energy with different frequencies.
Photons have the properties of both particles and waves. Since photons experience wave vibrations, the wavelength of light of the corresponding frequency is taken as the size of the photon.
The lantern is a source of white light. This is visible light, consisting of all sorts of 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 color, i.e. lack of color. Light passes through clear water without taking on any color.
But when light passes through water colored with milk, we notice that the water has become bluish, and the light spot on the screen turns yellow-orange. This happened as a result of scattering (deflection) 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 of about the same size as itself.
Small particles of milk in water scatter best the short wavelengths blue and violet. Thus, when white light passes through water tinted with milk, a pale blue sensation arises from the scattering of short wavelengths. After scattering on milk particles of short wavelengths from the light beam, mainly the wavelengths of yellow and orange... They move on to the screen.
If the particle size is greater than the maximum wavelength of visible light, the scattered light will be composed of all wavelengths; this light will be white.
Test 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.
Test 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 the light propagates in it.
Remember that the scattering of light in different substances can be compared by observing the brightness of these 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, you can compare, for example, the brightness of wet river sand with the brightness of dry sand. It should be borne in mind that the light falling on the dry sand passes through the air, and the light falling on the wet sand - through the water.
Pour sand into a disposable paper plate. Pour some water over the edge of the plate. Having noted the brightness of different areas of the sand in the plate, draw a conclusion in which sand the dispersion is greater: in dry (in which grains of sand are surrounded by air) or in wet (grains of sand are surrounded by water). You can try other liquids as well, such as vegetable oil.
Didactic material
Spreading light
As we know, one type of heat transfer is radiation. With 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 which is visible light.
The illuminated bodies gradually heat up. This means that light is really radiation.
Light phenomena are studied by a 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 humans. After all, more than ninety percent of information we receive thanks to 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, and glowing insects and plants. Artificial light sources are a candle, a lamp, a burner and many others.
Any light source consumes energy when emitting.
The sun emits light thanks to the energy from the nuclear reactions taking place in its depths.
A kerosene lamp converts the energy released during the combustion of kerosene into light.
Light reflection
A person sees a light source when a beam emanating from this source hits the eye. If the body is not a source, then the eye can perceive rays from any source, reflected by this body, that is, falling on the surface of this body and changing the direction of further propagation. A body that reflects rays becomes a source of reflected light.
The rays falling on the surface of the body change the direction of further propagation. When reflected, light returns to the same medium from which it fell onto the surface of the body. A body that reflects rays becomes a source of 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. Using a flat mirror, a simple experiment can be carried out to establish the law by which light is reflected. We place the illuminator on a sheet of paper lying on the table so 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.
Place a flat mirror vertically in the path of a thin light beam. A beam of light will bounce off it. You can make sure that the reflected beam, like the incident on the mirror, slides along the paper in the plane of the table. Mark with a pencil on a piece of paper the relative position of both light beams and the mirror. As a result, we will obtain a scheme of the experiment carried out. The angle between the incident beam and the perpendicular restored to the reflecting surface at the point of incidence is commonly 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 experiment are as follows:
- The incident beam, the reflected beam and the perpendicular to the reflecting surface, reconstructed at the point of incidence, lie in the same plane.
- Angle of incidence equal to the angle reflections. 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 are exactly the same. appearance items. It seems that these twin objects are located behind the surface of the mirror.
Consider an image of a point source in a flat mirror. To do this, we will randomly draw several rays from the source, construct the reflected rays corresponding to them, and then complete the extension of the reflected rays beyond the plane of the mirror. All the extensions of the rays will intersect behind the plane of the mirror at one point: this point is the image of the source.
Since in the image it is not the rays themselves that converge, but only their extensions, in reality there is no image at this point: it only seems to us that rays emanate from this point. Such an image is usually called imaginary.
Refraction of light
When the light reaches the separation of two media, part of it is reflected, while the other part passes through the border, refracting at the same time, that is, changing the direction of further propagation.
A coin immersed in water seems to us to be larger than when it is just lying on the table. A pencil or a spoon, placed in a glass of water, seems to us broken: the part 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 in different media, light propagates at different speeds.
The speed of propagation of light in a given 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 during the transition of light from air to water and during the transition from water to air? Experiments show that when passing from air to water, the angle of refraction turns out to be less than the angle of incidence. And vice versa: when passing from water to air, the angle of refraction turns out to be greater than the angle of incidence.
From experiments on light refraction, two facts became obvious: 1. The incident ray, the refracted ray and the perpendicular to the interface between the two media, reconstructed at the point of incidence, lie in the same plane.
- 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 going from an optically less dense medium to an optically denser one, 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 as 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 with an increase in the angle of incidence, the angle of refraction will also increase. At a certain value of the angle of incidence, the angle of refraction will be equal to 90 °.
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 equal to ninety degrees, the refracted ray 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. The use of flexible optical fibers is based on this phenomenon, through which light rays pass, being repeatedly reflected from the walls.
Light does not leave the fiber due to total internal reflection. A simpler optical device that uses total internal reflection is a reversing 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 surface of this lens is called thin. In what follows, we will only consider thin lenses. In optical schemes, thin lenses are depicted as segments with arrows at the ends. Depending on the direction of the arrows, the diagrams distinguish between collecting and diffusing lenses.
Consider how a beam of rays parallel to the main optical axis passes through the lens. Coming through
a collecting lens, the 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 extensions converge at one point lying in front of the lens.
The point at which, after refraction in a converging lens, beams parallel to the main optical axis are collected, is called the main focus of the lens-F.
In a diffusing lens, rays parallel to its main optical axis are scattered. The point at which the extensions of the refracted rays are collected lies in front of the lens and is called the main focus of the diffusing lens.
The focus of the scattering lens is obtained at the intersection of not the rays themselves, but their extensions, therefore, it is imaginary, in contrast to the converging lens, in which the focus is real.
The lens has two main focuses. 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 usually called the focal length of the lens. The more the lens changes the direction of the rays, the shorter 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 (diopter) is the optical power of a lens, the focal length of which is 1m. Since the focuses of the collecting lenses are real, and the scattering ones are imaginary, we agreed to consider the optical power of the collecting lenses a positive value, and the optical power of the scattering lenses negative
Who established the law of light reflection?
For the 16th century, optics was a cutting edge science. From a glass ball filled with water, which was used as a focusing lens, a magnifying glass emerged, and from it a microscope and a telescope. The largest naval power in those days, the Netherlands needed good telescopes in order to consider a dangerous coast ahead of time or to 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, Snell van Royen, who called himself Snellius (1580 - 1626), observed (which, however, many had seen before him), how a thin ray 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) and established the law: the angle of incidence is equal to the angle of reflection.
A source. Mirrored world. Gilde V. - M .: Mir, 1982. 24.
Why are diamonds so highly valued?
Obviously, a person especially highly values 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 not cut either), 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 type, is from 1.5 to 1.75).
White light is composed 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 the 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" bodies!
Experiments
EXPERIENCE in optics # 1
Explain the darkening of a block of wood after it has been wetted.
Equipment: a vessel with water, a wooden block.
Explain the oscillation of the shadow of a stationary object as 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 are added at different rotation modes. Explain the observed phenomenon.
EXPERIENCE # 2
By light interference.
Simple Demonstration of Light Absorption aqueous solution dye
Requires for its preparation only a school light, a glass of water and a white screen. Dyes can be very diverse, including fluorescent.
Students observe with great interest the color change of a white light beam as it propagates through the dye. The color of the beam emerging from the solution turns out to be unexpected for them. Since the light is focused by the illuminator lens, 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. (EXPERIENCE # 3)
What happens to the image of an object obtained with the lens if part of the lens is broken and the image is obtained with the rest of it?
Answer. The image will turn out in the same place where it was obtained with the whole lens, but its illumination will be less, because the smaller part of the rays coming out of the object will reach its image.
Place a small shiny object, such as a ball from a bearing or a bolt from a computer, on a table lit by the sun (or a powerful lamp) and look at it through a tiny hole in a piece of foil. Multi-colored rings, or ovals, will be clearly visible. What kind of phenomenon will be observed? Answer. Diffraction.
Simple experiments with colored glasses. (EXPERIMENT # 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 shards of bottle glass - green and red.
(Attention! Be careful, you can injure yourself on the edges of the debris!)
What glass do you need to look through to see an “Excellent” grade?
Answer. You must look through the green glass. In this case, the inscription will be visible in black on a green background of the paper, since the red light of the inscription “excellent” is not transmitted by the green glass. When viewed through red glass, the red lettering will not be visible on the red background of the paper.
EXPERIENCE # 5: Observing the phenomenon of dispersion
It is known that when a narrow beam of white light is passed through a glass prism, a rainbow strip can be observed on a screen mounted behind the prism, which is called the dispersion (or prismatic) spectrum. This spectrum is also observed when a light source, a prism and a screen are placed in a closed vessel from which air is evacuated.
The results of the last 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 dispersion of light 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 - a prism, and in the inscription on the monument there are the following words: "He investigated the difference between light rays and the various properties of flowers manifested at the same time, which no one had previously suspected."
EXPERIENCE # 6: Does a mirror have a memory?
How to put 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.
QUESTIONS
Transparent plexiglass becomes dull when rubbed with sandpaper. The same glass becomes transparent again if you rub it ...Than?
On the scale of the lens diaphragm, numbers are applied equal to the ratio of the focal length to the diameter of the hole: 2; 2.8; 4.5; five; 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 when photographing.
Most often, camera lenses consist of several lenses. Light passing through the lens is partially reflected from the lens surfaces. What defects does this lead to when shooting?Answer
When photographing snowy plains and water surfaces on sunny days, it is recommended to use a solar hood, which is a cylindrical or conical tube blackened inside, put on
lens. What is the purpose of the hood?Answer
To prevent light from reflecting inside the lens, a thinnest transparent film of the order of ten thousandths of a millimeter is applied to the surface of the lenses. Such lenses are called coated lenses. What physical phenomenon is lens enlightenment 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 does the white light, passing through the window glass, not decompose into its components?Answer.
Blitz
1. What are the glasses without temples called? (Pince-nez)
2. What gives out an eagle while hunting? (Shadow.)
3. What is the famous artist Quinji for? (Ability to portray the transparency of air and moonlight)
4. What are the names of the lamps that illuminate the stage? (Soffits)
5. Is it a blue or greenish gemstone?(Turquoise)
6. Indicate where 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, blue, violet)
3. Which is bigger: a cloud or a shadow from it? (The cloud casts a full shadow cone tapering to the ground, the height of which is large due to the large size of the cloud. Therefore, the cloud shadow differs little in size from the cloud itself)
4. You follow her, she is from you, you are from her, she is after you. What it is? (Shadow)
5. The edge is visible, but you won't get there. What is this? (Horizon)
Optical illusions.
Don't you think that black and white stripes are moving in opposite directions? If you tilt your head - now to the right, then to the left - the direction of rotation also changes.
Endless staircase leading up.
Sun and eye
do not be like the sun of the eyes,
He could not see the Sun ... W. Goethe
The juxtaposition of the eye and the sun is as old as the human race itself. The source of this comparison is not science. And in our time, next to science, simultaneously with the picture of phenomena revealed and explained by 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, which sometimes science does not yet suspect. In some cases, these connections are guessed correctly, sometimes they are fundamentally wrong 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 childhood, primitive and poetic ideas.
Playing hide and seek, a 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 preservation of the same instinctive confusion of sight and light in adults. Photographers, that is, people who are somewhat sophisticated in practical optics, often catch themselves closing their eyes when, when charging or developing the plates, you need to carefully monitor so that light does not penetrate into a dark room.
If you listen carefully to how we speak, to our own words, then here, too, traces of the same fantastic optics are immediately discovered.
Without noticing this, people say: "the eyes sparkled", "the sun has peeped out", "the stars are watching."
For poets, transferring visual representations to a luminary and, conversely, attributing the properties of light sources to the eyes is the most common, one might say, mandatory technique:
The stars of the night
Like accusatory eyes
They are looking at him mockingly.
His eyes are shining.
A.S. Pushkin.
We looked at the stars with you
They are on us. Fet.
How does a fish see you?
Because of the refraction of light, the fisherman sees the fish not where it really is.
Folk omens
Introduction
1.Literary 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 experimental technique
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, and 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, in accordance with which experiment is the basis for cognition of phenomena. Demonstration experiments contribute to the creation of physical concepts. Among the 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 illustrative and interesting experiments in optics were selected using equipment that can be purchased by any school or made independently.
Literature review
1.1 The history of the development of geometric optics.
Optics belongs to such sciences, the initial ideas of which arose in ancient times. Throughout its centuries-old history, it has experienced continuous development, and at present it is one of the fundamental physical sciences, enriching itself with the discoveries of more and more 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 light appeared 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 from the fact that "hot vapors" emanate from the eyes to objects. In their further development, these views took on 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" emanate from the eyes, which feel with their ends of the body 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 light reflection 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 found by Euclid are preserved in modern geometric optics. The refraction of light was also familiar to Euclid. 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 failed 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 knew the effect of concave mirrors. Archimedes (287-212 BC) is credited with burning the enemy fleet using a system of concave mirrors, which he used to collect the sun's rays and direct it to Roman ships. A certain step forward was made by Empedocles (492-432 BC), who believed that outflows are directed from luminous bodies to the eyes, and outflows emanate from the eyes toward the bodies. When these outflows meet, visual sensations arise. The famous Greek philosopher, founder of atomism, Democritus (460-370 BC) completely rejects the concept of visual rays. According to the views of Democritus, vision is due to the fall on the surface of the eye of small atoms emanating from objects. Epicurus (341-270 BC) later adhered to similar views. The famous Greek philosopher Aristotle (384-322 BC), who believed that the cause of visual sensations lies outside the human eye, was also a decisive opponent of the "theory of visual rays". Aristotle made an attempt to explain colors as a consequence of the mixture of light and darkness.
It should be noted that the views of ancient thinkers were mainly based on the simplest 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 for the most part only ingenious guesses, they certainly had a great influence on the further development of optics.
The Arab physicist Algazen (1038) developed a number of problems in optics in his research. He studied the eye, refraction of light, reflection of light in concave mirrors. When studying the refraction of light, Algazey, 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. Algazen knows the magnifying power of spherical glass segments. On the question of the nature of light, Alhazen takes the right positions, 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 has a finite speed of propagation, which in itself represents a major step in understanding the nature of light. Alhazen correctly explained that the Sun and Moon appear larger on the horizon than at their zenith; he attributed this to a deception of the senses.
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 Mavrolik (1494-1575) is credited with a fairly accurate explanation of the glasses. Mavrolik also found that concave lenses do not collect but scatter rays. He found that the lens is the most important part of the eye, and made a conclusion about the causes of hyperopia and myopia as a consequence of the abnormal refraction of light by the lens. Next, we should mention the Italian Port (1538-1615), who in 1589 invented the camera obscura - the prototype of the future camera. A few years later, the main 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. Telescopes began to be produced at about the same time (1608-1610) by Dutch opticians Zachary Jansen, Jacob Metzius and Hans Lippersgey. The invention of these optical instruments led in the following years to major discoveries in astronomy and biology. The German physicist and astronomer N. Kepler (1571-1630) carried out fundamental work 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 light refraction.
Fermat's principle, named after the French scientist Pierre Fermat (1601-1665), who formulated it, was of great importance for geometric optics. This principle established that light between two points spreads along such a path, which takes a minimum of time to travel. It follows from this that Fermat, in contrast to Descartes, considered the speed of propagation of light to be finite. The famous Italian physicist Galilei (1564-1642) did not carry out systematic work devoted to the study of light phenomena. However, in optics, he also owns works that have brought science remarkable results. Galileo improved the telescope and first applied it to astronomy, in which he made outstanding discoveries that contributed to the substantiation of the latest views on the structure of the Universe, based on the Copernican heliocentric system. Galileo managed to create a telescope with a frame magnification of 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 in terrestrial conditions, but was unsuccessful due to the weakness of the experimental means available for this purpose ... Hence it follows that Galileo already had the correct idea of the final speed of light propagation. Galileo also observed sunspots. The priority of the discovery of sunspots by Galileo was challenged by the Jesuit scientist Pater Scheiner (1575-1650), who made accurate observations of sunspots and solar torches using a telescope arranged according to Kepler's scheme. 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 get an image of the Sun on the screen and demonstrate it at different degrees of magnification to several faces 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 the property of wider circles, which contributes to the establishment of international relations in science. In the second half of the 17th century, the experimental method of studying natural phenomena finally won out.
The largest discoveries of this period are associated with the name of the brilliant English physicist and mathematician Isaac Newton / (1643-1727). The most important experimental discovery of Newton in optics is the dispersion of light in a prism (1666). Investigating the passage of a beam of white light through a triangular prism, Newton found that a beam of white light splits into an infinite set of colored rays that form a continuous spectrum. From these experiments it was concluded that white light is a complex radiation. Newton also made the opposite experiment, collecting with the help of a lens colored rays formed after a ray of white light passed through a prism. As a result, he again received white light. Finally, Newton conducted an experiment of color mixing using a rotating circle divided into several sectors, colored in the primary colors of the spectrum. When the disc rotated quickly, all the colors merged into one, giving the impression of white.
The results of these fundamental experiments Newton laid the foundation for the theory of colors, which had not been possible before by any of his predecessors. According to the theory of colors, 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 concept of light rays as straight lines along which light energy propagates, is called geometric optics. This name was given to it because all the phenomena of the propagation of light here can be investigated by means of geometric constructions of the path of rays, taking into account the law of reflection and refraction of light. This law is the foundation of geometric optics.
However, where it comes about phenomena, the interaction of light with obstacles, the dimensions of which are small enough, 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 the reflection of light from mirrors. The concept of a light ray as an infinitely thin beam of light propagating rectilinearly 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 make it possible to carry out calculations and design of optical devices. All these laws were initially established as empirical, that is, based on experiments, observations.
Broken pencil
Arrow experiment
This will surprise not only children, but also adults!
With children, you can still conduct 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 in which water is more?
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, move the rest apart so that this row is the same in length as the top one. And again ask if it is the same now, etc. Give it a try - the answers will surely surprise you!
Ebbinghaus illusion (Ebbinghaus) or Titchener's circles- optical illusion of perception of relative sizes. The most famous 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; the first circle seems to be smaller than the second.
The two orange circles are perfectly the same size; however, the left circle appears to be smaller
Mueller-Lyer illusion
The illusion is that the segment framed by the “points” appears to be shorter than the segment framed by the “tail” arrows. The illusion was first described by German psychiatrist Franz Müller-Lyer in 1889
Or else, for example, an optical illusion - first you see black, then white
Even more optical illusions
And finally, the toy-illusion - Thaumatrope.
When you rotate a small piece of paper quickly with two drawings on different sides, 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 bank) on thick enough paper and attach strings 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 sets for experiments in the field of optical illusions!
Introduction
Without a doubt, all our knowledge begins with experience.
(Kant Emmanuel. German philosopher 1724-1804)
Physics experiments in an entertaining way familiarize students with the various applications of the laws of physics. Experiments can be used in the classroom to draw the attention of students to the phenomenon being studied, while repeating and consolidating educational material, at physical evenings. Entertaining experiences deepen and expand the knowledge of students, contribute to the development of logical thinking, instill an 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 the secondary school No. 1, Zabaikalsk, Zabaikalsky Krai - Chuguevsky Artyom, Lavrentyev Arkady, Chipizubov Dmitry. The guys independently performed these experiments, summarized the results and presented them in the form of this work
The role of experiment in science physics
That physics is a young science
To say for sure, it is impossible here
And in ancient times, knowing science,
We always tried to comprehend it.The goal of teaching physics is specific,
To be able to apply all knowledge in practice.
And it's important to remember - the role of experiment
Should stand in the first place.Be able to plan and execute an experiment.
Analyze and bring to life.
Build a model, put forward a hypothesis,
Strive to reach new heights
The laws of physics are based on empirically established facts. Moreover, the interpretation of the same facts often changes in the course of the historical development of physics. Facts accumulate through observation. But at the same time, one cannot be limited only to them. This is only the first step towards knowledge. Next comes the experiment, the development of concepts that allow for qualitative characteristics. In order to draw general conclusions from observations, to find out the causes of the phenomena, it is necessary to establish quantitative relationships between the 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 an experiment in each individual case, it is enough to perform the appropriate calculations. Having studied experimentally the quantitative relationships between quantities, it is possible to identify patterns. On the basis of these regularities, a general theory of phenomena is being developed.
Therefore, there can be no rational teaching of physics without experiment. The study of physics presupposes extensive use of the experiment, 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:
- Experience name
- Devices and materials required for experience
- Stages of the experiment
- Explaining the experience
Experience No. 1 Four floors
Appliances 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 don't mix and stand five stories above the other. However, it will be more convenient for us to take not a glass, but a narrow glass that expands to the top.
- Pour salted tinted water to the bottom of the glass.
- Roll "Funtik" out of paper and bend its end at a right angle; cut off the tip. The hole in the Funtik should be about the size of a pinhead. Pour red wine into this horn; a thin stream should flow out of it horizontally, break against the walls of the glass and drain 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. - Pour the sunflower oil into a glass from the second horn in the same way.
- Pour a layer of colored alcohol from the third horn.
Picture 1
So we got four floors of liquids in one glass. All of different colors and different densities.
Explaining the experience
The liquids in the grocery are 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 density.
Experience # 2 Amazing candlestick
Appliances 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 candle is completely immersed in water, only the wick and the very tip of the paraffin should protrude above the water.
- Light the fuse.
Explaining the experience
Let them tell you, because in a minute the candle will burn out to the water and go out!
The fact of the matter, you will answer, is that the candle is shorter by the minute. And if it is shorter, then it is easier. If it's easier, then it will float up.
And, it is true, the candle will float up a 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 forms around the wick. This emptiness, in turn, makes the candle lighter, which is why our candle will burn out to the end.
Experience number 3 Candle by bottle
Appliances and materials: candle, bottle, matches
Stages of the experiment
- Put a lighted candle behind the bottle, and stand yourself so that your face is 20-30 cm from the bottle.
- It is worth blowing now, and the candle will go out, as if there is no barrier between you and the candle.
Figure 3
Explaining the experience
The candle goes out because the bottle is “flown around” by the air: the air stream is broken by the bottle into two streams; one flows around it on the right, and the other on the left; and they are found approximately where there is a candle flame.
Experience number 4 Swirling snake
Appliances and materials: thick paper, candle, scissors.
Stages of the experiment
- Cut a spiral out of thick paper, stretch it slightly and place it on the end of the curved wire.
- By holding this spiral above the candle in an upward flow of air, the snake will rotate.
Explaining the experience
The snake rotates because there is an expansion of air under the influence of heat and the transformation of warm energy into movement.
Figure 4
Experience number 5 The eruption of Vesuvius
Devices and materials: glass vessel, vial, cork, alcohol ink, water.
Stages of the experiment
- Put a bottle of alcohol mascara in a wide glass vessel filled with water.
- There should be a small hole in the bubble stopper.
Figure 5
Explaining the experience
Water has a higher density than alcohol; it will gradually enter the bubble, displacing the mascara from there. Red, blue or black liquid will rise up from the bubble in a thin stream.
Experience number 6 Fifteen matches on one
Apparatus and materials: 15 matches.
Stages of the experiment
- Put one match on the table, and 14 matches across it so that their heads stick out upward, and the ends touch the table.
- How to pick up the first match, holding it by one end, and with it all the other matches?
Explaining the experience
To do this, you only need to put another, fifteenth match on top of all the matches, in the hollow between them
Figure 6
Experiment No. 7 Pot holder
Appliances and materials: plate, 3 forks, napkin ring, saucepan.
Stages of the experiment
- Place three forks in the ring.
- Put a plate on this structure.
- Place a pot of water on a stand.
Figure 7
Figure 8
Explaining the experience
This experience is explained by the rule of leverage and stable equilibrium.
Figure 9
Experience number 8 Paraffin motor
Appliances and materials: candle, knitting needle, 2 glasses, 2 plates, matches.
Stages of the experiment
We don't need electricity or gas to make this motor. 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 the candle with a knitting needle on the edges of two glasses and balance.
- Light a candle at both ends.
Explaining the experience
A drop of paraffin will fall into one of the plates placed under the ends of the candle. The balance will be violated, the other end of the candle will pull and drop; 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, become lighter, and our motor will start to work with might and main; gradually, the fluctuations of the candle will increase more and more.
Figure 10
Experience No. 9 Free exchange of fluids
Appliances 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 skin peels off with a whole cup.
- Poke two holes next to it in the bottom of this cup and put it in the glass. The diameter of the cup should be slightly larger than the diameter of the central part of the glass, then the cup will hold onto the walls without falling to the bottom.
- Dip the orange cup into the vessel one third of its height.
- Pour red wine or tinted alcohol into the orange peel. It will go through the hole until the wine level reaches the bottom of the cup.
- Then pour water almost to the brim. You can see how the stream of wine rises through one of the holes to the water level, while the heavier water will pass through the other hole and begin to sink to the bottom of the glass. In a few moments, the wine will be at the top, and the water will be below.
Experience number 10 Singing glass
Appliances and materials: thin glass, water.
Stages of the experiment
- Fill the glass with water and wipe the edges of the glass.
- Rub the glasses with a moistened finger anywhere, she will sing.
Figure 11
Demonstration experiments
1. Diffusion of liquids and gases
Diffusion (from the Latin diflusio - spreading, spreading, scattering), the transfer of particles of different nature, due to the chaotic thermal movement of molecules (atoms). Distinguish between diffusion in liquids, gases and solids
Demonstration experiment "Observation of diffusion"
Devices and materials: cotton wool, ammonia, phenolphthalein, installation for observing diffusion.
Experiment steps
- Take two pieces of cotton wool.
- Soak one piece of cotton wool with phenolphthalein, the other with ammonia.
- Let's bring the branches into contact.
- 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
- Pour ammonia into one of the cones.
- Soak a piece of cotton wool with phenolphthalein and place it on top of a cone.
- 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 the diffusion proceeds.
Figure 16
To demonstrate this experience, let's take two identical glasses. Pour cold water into one glass, hot water into the other. Add copper sulfate to the glasses, we 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
We will pour liquid into one of them: we will immediately find that the liquid will flow through the tubes into the other 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 must be in the same horizontal plane: otherwise, the kettle cannot be poured to the top.
Figure 21
3 Pascal's ball
Pascal ball is a device designed to demonstrate the uniform transmission of pressure produced on a liquid or gas in a closed vessel, as well as the rise of liquid behind the piston under the influence of atmospheric pressure.
To demonstrate the uniform transmission of the pressure produced on the liquid in a closed vessel, it is necessary, using a piston, to draw water into the vessel and tightly put a ball on the branch pipe. 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.
