The basic formulas in physics are optics. Optics is a branch of physics that studies the behavior and properties of light.

We come across the word "optics", for example, when we pass by a point of sale where glasses are sold. Also, many remember that they studied optics at school. What is optics?

Optics is a branch of physics that studies the nature of light, its properties, the laws of propagation in various media, as well as the interaction of light with substances. To better understand what optics is, you need to understand what light is.

Light concepts in modern physics

Physics regards light, familiar to us, as a complex phenomenon with a dual nature. On the one hand, light is considered to be a stream of tiny particles - quanta of light (photons). On the other hand, light can be described as a kind of electromagnetic waves with a specific length.

Separate sections of optics study light as a physical phenomenon from various angles.

Optics Sections

Geometric optics. Considers the laws of propagation of light, as well as the reflection and refraction of light rays. Represents light as a ray propagating in a homogeneous medium in a rectilinear manner (in this it is similar to a geometric ray). Does not take into account the wave nature of light.
Wave optics. Studies the properties of light as a kind of electromagnetic waves.
Quantum optics. Studies the quantum properties of light (studies the photoelectric effect, photochemical processes, laser radiation, etc.)

Optics in human life

Studying the nature of light and the laws of its propagation, a person uses the knowledge gained to his advantage. The most common optical devices in the surrounding life are glasses, a microscope, a telescope, a photo lens, as well as a fiber optic cable used for laying a LAN (you can find out about this in the article

- The history of the development of optics.

- The main provisions of the corpuscular theory of Newton.

- The main provisions of Huygens' wave theory.

- Views on the nature of light in XIX – XX centuries.

- The main provisions of optics.

- Wave properties of light and geometric optics.

- The eye as an optical system.

- Spectroscope.

- Optical measuring device.

- Conclusion.

- List of used literature.

The history of the development of optics.

Optics - the study of the nature of light, light phenomena and the interaction of light with matter. And almost all of her story is a story of searching for an answer: what is light?

One of the first theories of light, the theory of visual rays, was put forward by the Greek philosopher Plato around 400 BC. NS. This theory assumed that rays emanate from the eye, which, meeting with objects, illuminate them and create the appearance of the surrounding world. Plato's views were supported by many scientists of antiquity and, in particular, Euclid (3rd century BC), based on the theory of visual rays, founded the doctrine of the straightness of the propagation of light, established the law of reflection.

In the same years, the following facts were discovered:

- straightness of light propagation;

- the phenomenon of light reflection and the law of reflection;

- the phenomenon of light refraction;

- focusing action of a concave mirror.

The ancient Greeks laid the foundation for the branch of optics, which later received the name geometric.

The most interesting work on optics that has come down to us from the Middle Ages is the work of the Arab scientist Algazen. He studied the reflection of light from mirrors, the phenomenon of refraction and transmission of light in lenses. Alhazen was the first to express the idea that light has a finite speed of propagation. This hypothesis was a major

a step in understanding the nature of light.

During the Renaissance, many different discoveries and inventions were made; the experimental method began to establish itself as the basis for the study and knowledge of the surrounding world.

On the basis of numerous experimental facts in the middle of the 17th century, two hypotheses arose about the nature of light phenomena:

- corpuscular, which assumed that light is a stream of particles ejected at high speed by luminous bodies;

- wave, which asserted that light is a longitudinal vibrational motion of a special luminiferous medium - ether - excited by vibrations of particles of a luminous body.

All further development of the theory of light up to the present day is the history of the development and struggle of these hypotheses, the authors of which were I. Newton and H. Huygens.

The main provisions of Newton's corpuscular theory:

1) Light consists of small particles of matter, emitted in all directions along straight lines, or rays, a luminous body, for example, a burning candle. If these rays, consisting of corpuscles, fall into our eye, then we see their source (Fig. 1).

2) Light corpuscles have different sizes. The largest particles, entering the eye, give the impression of a red color, the smallest - violet.

3) White is a mixture of all colors: red, orange, yellow, green, light blue, blue, purple.

4) Reflection of light from the surface occurs due to the reflection of corpuscles from the wall according to the law of absolute elastic impact (Fig. 2).

5) The phenomenon of light refraction is explained by the fact that corpuscles are attracted by particles of the medium. The denser the medium, the less the angle of refraction is the angle of incidence.

6) The phenomenon of dispersion of light, discovered by Newton in 1666, he explained as follows. Every color is already present in white light. All colors are transmitted through interplanetary space and atmosphere together and produce a white light effect. White light - a mixture of various corpuscles - experiences refraction after passing through a prism. From the point of view of mechanical theory, refraction is due to the forces from the glass particles acting on the light corpuscles. These forces are different for different corpuscles. They are largest for purple and smallest for red. The path of the corpuscles in the prism for each color will be refracted in its own way, therefore the white complex ray will split into colored component rays.

7) Newton outlined the ways of explaining birefringence, hypothesizing that the rays of light have "different sides" - a special property that determines their different refraction when passing through a birefringent body.

Newton's corpuscular theory satisfactorily explained many optical phenomena known at that time. Its author enjoyed tremendous authority in the scientific world, and soon Newton's theory gained many supporters in all countries.

The main provisions of Huygens' wave theory of light.

1) Light is the propagation of elastic periodic impulses in the ether. These impulses are longitudinal and similar to impulses of sound in air.

2) Ether is a hypothetical medium that fills the heavenly space and the gaps between the particles of bodies. It is weightless, does not obey the law of universal gravitation, and has great elasticity.

3) The principle of propagation of vibrations of the ether is such that each point, to which the excitation reaches, is the center of secondary waves. These waves are weak, and the effect is observed only where their envelope passes.

surface - wave front (Huygens principle) (Fig. 3).

Light waves coming directly from the source produce the sensation of seeing.

A very important point in Huygens' theory was the assumption that the speed of light propagation was finite. Using his principle, the scientist was able to explain many of the phenomena of geometric optics:

- the phenomenon of light reflection and its laws;

- the phenomenon of light refraction and its laws;

- the phenomenon of total internal reflection;

- the phenomenon of birefringence;

- the principle of independence of light rays.

Huygens' theory gave the following expression for the refractive index of a medium:

The formula shows that the speed of light should depend inversely on the absolute index of the medium. This conclusion was the opposite of the conclusion following from Newton's theory. The low level of experimental technology in the 17th century made it impossible to establish which theory was correct.

Many doubted Huygens' wave theory, but among the few supporters of wave views on the nature of light were M. Lomonosov and L. Euler. With the research of these scientists, the theory of Huygens began to take shape as a theory of waves, and not just aperiodic oscillations propagating in the ether.

Views on the nature of light in XIX - XX centuries.

In 1801, T. Jung performed an experiment that amazed the world's scientists (Fig. 4)

S - light source;

E - screen;

B and C are very narrow slits spaced 1-2 mm apart.

According to Newton's theory, two light stripes should appear on the screen, in fact, several light and dark stripes appeared, and a light line P appeared directly opposite the gap between the slots B and C. Experience showed that light is a wave phenomenon. Jung developed Huygens' theory with ideas about the vibrations of particles, about the frequency of vibrations. He formulated the principle of interference, based on which he explained the phenomenon of diffraction, interference and color of thin plates.

The French physicist Fresnel combined Huygens' principle of wave motion and Young's interference principle. On this basis, he developed a rigorous mathematical theory of diffraction. Fresnel was able to explain all the optical phenomena known at that time.

The main provisions of the Fresnel wave theory.

- Light - the propagation of vibrations in the ether at a speed where the elastic modulus of the ether, r- the density of the ether;

- Light waves are transverse;

- The light ether has the properties of an elastic-solid body, it is absolutely incompressible.

When passing from one medium to another, the elasticity of the ether does not change, but its density changes. The relative refractive index of the substance.

Lateral vibrations can occur simultaneously in all directions perpendicular to the direction of wave propagation.

Fresnel's work won the recognition of scientists. Soon a whole series of experimental and theoretical works appeared, confirming the wave nature of light.

In the middle of the 19th century, facts began to emerge indicating a connection between optical and electrical phenomena. In 1846 M. Faraday observed the rotation of the planes of polarization of light in bodies placed in a magnetic field. Faraday introduced the concept of electric and magnetic fields as a kind of superposition in the ether. A new "electromagnetic ether" has appeared. The first to draw attention to these views was the English physicist Maxwell. He developed these ideas and built a theory of the electromagnetic field.

The electromagnetic theory of light did not eliminate the mechanical theory of Huygens-Jung-Fresnel, but raised it to a new level. In 1900, the German physicist Planck put forward a hypothesis about the quantum nature of radiation. Its essence was as follows:

- light emission is discrete;

- absorption also occurs in discrete portions, quanta.

The energy of each quantum is represented by the formula E = h n, where h Is Planck's constant, and n Is the frequency of the light.

Five years after Planck, the work of the German physicist Einstein on the photoelectric effect came out. Einstein believed:

- light that has not yet entered into interaction with matter has a granular structure;

- the structural element of discrete light radiation is a photon.

Thus, a new quantum theory of light appeared, which was born on the basis of Newton's corpuscular theory. A quantum acts as a corpuscle.

Basic provisions.

- Light is emitted, distributed and absorbed in discrete portions - quanta.

- Quantum of light - a photon carries energy proportional to the frequency of the wave with which it is described by the electromagnetic theory E = h n .

- Photon, has mass (), momentum and angular momentum ().

- A photon, as a particle, exists only in motion, the speed of which is the speed of propagation of light in a given environment.

- For all interactions in which a photon participates, the general laws of conservation of energy and momentum are valid.

- An electron in an atom can only be in some discrete stable stationary states. While in stationary states, the atom does not radiate energy.

- When passing from one stationary state to another, an atom emits (absorbs) a photon with a frequency, (where E1 and E2- energies of the initial and final states).

With the emergence of quantum theory, it became clear that the corpuscular and wave properties are only two sides, two interrelated manifestations of the essence of light. They do not reflect the dialectical unity of discreteness and continuity of matter, expressed in the simultaneous manifestation of wave and corpuscular properties. One and the same radiation process can be described both with the help of a mathematical apparatus for waves propagating in space and time, and with the help of statistical methods for predicting the appearance of particles in a given place and at a given time. Both of these models can be used at the same time, and depending on the conditions, preference is given to one of them.

The achievements of recent years in the field of optics have become possible thanks to the development of both quantum physics and wave optics. The theory of light continues to evolve today.

Optics is a branch of physics that studies the properties and physical nature of light, as well as its interaction with matter.

The simplest optical phenomena, such as the appearance of shadows and the acquisition of images in optical devices, can be understood within the framework of geometric optics, which operates with the concept of separate light rays obeying the known laws of refraction and reflection and independent of each other. To understand more complex phenomena, physical optics is needed, which considers these phenomena in connection with the physical nature of light. Physical optics makes it possible to derive all the laws of geometric optics and establish the limits of their applicability. Without knowledge of these boundaries, the formal application of the laws of geometric optics can, in specific cases, lead to results that contradict the observed phenomena. Therefore, one cannot confine oneself to the formal construction of geometric optics, but it is necessary to look at it as a section of physical optics.

The concept of a light beam can be obtained from the consideration of a real light beam in a homogeneous medium, from which a narrow parallel beam is extracted with the help of a diaphragm. The smaller the diameter of these holes, the narrower the emitted beam, and in the limit, passing to holes as small as you like, one would see the light beam as a straight line. But such a process of extracting an arbitrarily narrow beam (ray) is impossible due to the phenomenon of diffraction. The inevitable angular expansion of a real light beam transmitted through a diaphragm of diameter D is determined by the diffraction angle j ~ l / D... Only in the limiting case when l= 0, such an expansion would not take place, and one could speak of a ray as a geometric line, the direction of which determines the direction of propagation of light energy.

Thus, a light ray is an abstract mathematical concept, and geometrical optics is an approximate limiting case into which wave optics goes when the length of a light wave tends to zero.

The eye as an optical system.

The human organ of vision is the eyes, which in many respects represent a very perfect optical system.

In general, the human eye is a spherical body about 2.5 cm in diameter, which is called the eyeball (Fig. 5). The opaque and durable outer shell of the eye is called the sclera, and its transparent and more convex anterior part is called the cornea. On the inside, the sclera is covered with a choroid, which consists of blood vessels that feed the eye. Against the cornea, the choroid passes into the iris, which is unequally colored in different people, which is separated from the cornea by a chamber with a transparent watery mass.

The iris has a circular opening called the pupil, which can vary in diameter. Thus, the iris acts as a diaphragm that regulates the access of light to the eye. In bright light, the pupil decreases, and in low light, it increases. Inside the eyeball, behind the iris, the lens is located, which is a biconvex lens made of transparent material with a refractive index of about 1.4. The lens is surrounded by an annular muscle, which can change the curvature of its surfaces, and hence its optical power.

The choroid on the inner side of the eye is covered with branches of the photosensitive nerve, especially dense opposite the pupil. These ramifications form a reticular membrane on which the actual image of objects is obtained, created by the optical system of the eye. The space between the retina and the lens is filled with a transparent vitreous body with a gelatinous structure. The image of objects on the retina is inverted. However, the activity of the brain, which receives signals from the light-sensitive nerve, allows us to see all objects in natural positions.

When the annular muscle of the eye is relaxed, then the image of distant objects is obtained on the retina. In general, the structure of the eye is such that a person can see without tension objects located at least 6 meters from the eye. In this case, the image of closer objects is obtained behind the retina of the eye. To obtain a clear image of such an object, the annular muscle compresses the lens more and more until the image of the object is on the retina, and then holds the lens in a compressed state.

Thus, the "focusing" of the human eye is carried out by changing the optical power of the lens with the help of the annular muscle. The ability of the optical system of the eye to create clear images of objects located at different distances from it is called accommodation (from the Latin "accommodation" - adaptation). When looking at very distant objects, parallel rays fall into the eye. In this case, the eye is said to be accommodated to infinity.

The accommodation of the eye is not infinite. With the help of the annular muscle, the optical power of the eye can be increased by no more than 12 diopters. With a long examination of close objects, the eyes get tired, and the annular muscle begins to relax and the image of the object becomes blurred.

Human eyes allow you to see objects well, not only in daylight. The ability of the eye to adapt to varying degrees of irritation of the endings of the photosensitive nerve on the retina, i.e. to varying degrees of brightness of the observed objects is called adaptation.

The convergence of the visual axes of the eyes at a certain point is called convergence. When objects are located at a considerable distance from a person, then when moving the eyes from one object to another between the axes of the eyes, it practically does not change, and the person loses the ability to correctly determine the position of the object. When objects are very far away, the axes of the eyes are parallel, and the person cannot even determine whether the object is moving or not, at which he is looking. The force of the annular muscle, which compresses the lens when examining objects located near the person, also plays a role in determining the position of the bodies. sheep.

Spectrum oskop.

A spectroscope is used to observe the spectra.

The most common prismatic spectroscope consists of two tubes, between which a triangular prism is placed (Fig. 7).

In tube A, called a collimator, there is a narrow slit, the width of which can be adjusted by turning the screw. A light source is placed in front of the slit, the spectrum of which must be investigated. The slit is located in the plane of the collimator, and therefore the light rays from the collimator come out in the form of a parallel beam. After passing through the prism, the light rays are directed into the tube B, through which the spectrum is observed. If the spectroscope is intended for measurements, then an image of a scale with divisions is superimposed on the spectrum image using a special device, which allows you to accurately establish the position of the color lines in the spectrum.

Optical measuring device - a measuring instrument in which sighting (aligning the boundaries of the controlled object with a target line, crosshair, etc.) or determining the size is carried out using a device with an optical principle of operation. There are three groups of optical measuring instruments: instruments with an optical principle of sight and a mechanical way of reporting the movement; instruments with optical sighting and movement reporting; devices having mechanical contact with a measuring device, with an optical method for determining the movement of contact points.

Of the devices, projectors for measuring and controlling parts with a complex contour and small dimensions were the first to spread.

The second most common instrument is a universal measuring microscope, in which the part to be measured moves on a longitudinal carriage, and the head microscope - on a transverse one.

Devices of the third group are used to compare measured linear quantities with measures or scales. They are usually grouped together under the general name comparators. This group of devices includes an optimeter (opticator, measuring machine, contact interferometer, optical rangefinder, etc.).

Optical measuring instruments are also widely used in geodesy (level, theodolite, etc.).

Theodolite is a geodetic instrument for determining directions and measuring horizontal and vertical angles in geodetic works, topographic and mine surveying, in construction, etc.

Level - a geodetic tool for measuring the elevations of points on the earth's surface - leveling, as well as for setting horizontal directions during assembly, etc. works.

In navigation, a sextant is widespread - a goniometric mirror-reflective instrument for measuring the heights of celestial bodies above the horizon or the angles between visible objects in order to determine the coordinates of the observer's place. The most important feature of the sextant is the ability to combine two objects in the observer's field of view at the same time, between which the angle is measured, which makes it possible to use the sextant on an airplane and on a ship without a noticeable decrease in accuracy even during rolling.

A promising direction in the development of new types of optical measuring devices is equipping them with electronic reading devices, which make it possible to simplify the reading and sighting, etc.

Conclusion.

The practical significance of optics and its influence on other branches of knowledge are exceptionally great. The invention of the telescope and spectroscope opened before man the most amazing and richest world of phenomena occurring in the vast universe. The invention of the microscope revolutionized biology. Photography has helped and continues to help almost all branches of science. One of the most important elements of scientific equipment is the lens. Without it there would be no microscope, telescope, spectroscope, camera, cinema, television, etc. there would be no glasses, and many people over 50 years old would be deprived of the opportunity to read and perform many of the work related to vision.

The field of phenomena studied by physical optics is very extensive. Optical phenomena are closely related to phenomena studied in other branches of physics, and optical research methods are among the most subtle and accurate. Therefore, it is not surprising that for a long time optics played a leading role in very many fundamental research and the development of basic physical views. Suffice it to say that both the main physical theories of the last century - the theory of relativity and the theory of quanta - originated and largely developed on the basis of optical research. The invention of lasers opened up new vast possibilities not only in optics, but also in its applications in various branches of science and technology.

Moscow Education Committee

World About R T

Moscow technological college

Department of Natural Sciences

Final work in physics

On the topic :

Performed by a student of group 14: Ryazantseva Oksana

Teacher: Gruzdeva L.N.

- Artsybyshev S.A. Physics - M .: Medgiz, 1950.

- Zhdanov L.S. Zhdanov G.L. Physics for secondary educational institutions - Moscow: Nauka, 1981.

- Landsberg G.S. Optics - Moscow: Nauka, 1976.

- Landsberg G.S. Elementary physics textbook. - M .: Nauka, 1986.

- A.M. Prokhorov Great Soviet Encyclopedia. - M .: Soviet Encyclopedia, 1974.

- Sivukhin D.V. General course of physics: Optics - Moscow: Nauka, 1980.

Here are the notes on physics on the topic "Optics" for grades 10-11.
!!! Abstracts with the same title vary in degree of difficulty.

3. Light diffraction- Wave optics

4. Mirrors and lenses- Geometric optics

5. Light interference- Wave optics

6. Light polarization- Wave optics

Optics, geometric optics, wave optics, grade 11, notes, notes on physics.

ABOUT COLOR. DID YOU KNOW?

Did you know that a piece of red glass appears red in both reflected and transmitted light. But in non-ferrous metals, these colors differ - for example, gold reflects mainly red and yellow rays, but a thin translucent gold plate transmits green light.

Scientists of the 17th century did not consider color to be an objective property of light. For example, Kepler believed that color is a quality that philosophers should study, not physicists. And only Descartes, although he could not explain the origin of flowers, was convinced of the existence of a connection between them and the objective characteristics of light.

The wave theory of light created by Huygens was a big step forward - for example, it gave the explanations of the laws of geometric optics used until now. However, its main failure was the absence of a color category, i.e. it was the theory of colorless light, despite the discovery already made by Newton by that time — the discovery of the dispersion of light.

The prism - the main instrument in Newton's experiments - was bought by him in a pharmacy: in those days, observing prismatic spectra was a widespread entertainment.

Many of Newton's predecessors believed that colors originated in the prisms themselves. Thus, Newton's constant opponent, Robert Hooke, thought that the sun's ray could not contain all colors; it was as strange, he thought, as to say that "the air of organ bellows contains all the tones."

Newton's experiments led him to a sad conclusion: in complex devices with a large number of lenses and prisms, the decomposition of white light is accompanied by the appearance of a motley colored border in the image. The phenomenon, called "chromatic aberration", was subsequently overcome by combining multiple layers of glass with "counterbalancing" refractive indices, resulting in achromatic lenses and spotting scopes with clear images without colored glare and streaks.

The idea that color is determined by the frequency of vibrations in a light wave was first expressed by the famous mathematician, mechanic and physicist Leonard Euler in 1752, with the maximum wavelength corresponding to red rays, and the minimum to violet.

Initially, Newton distinguished only five colors in the solar spectrum, but later, seeking a correspondence between the number of colors and the number of fundamental tones of the musical scale, he added two more. Perhaps this was due to the addiction to the ancient magic of the number "seven", according to which there were seven planets in the sky, and therefore there are seven days in a week, seven basic metals in alchemy, and so on.

Goethe, who considered himself an outstanding natural scientist and a mediocre poet, hotly criticizing Newton, noticed that the properties of light revealed in his experiments were not true, since the light in them was "tortured by all sorts of instruments of torture - slits, prisms, lenses." True, in this criticism, quite serious physicists later saw a naive anticipation of the modern point of view on the role of measuring equipment.

The theory of color vision - about obtaining all colors by mixing three main ones - originates from Lomonosov's speech in 1756 "A word about the origin of light, a new theory of colors representing ...", which, however, was not noticed by the scientific world. Half a century later, this theory was supported by Jung, and even his assumptions in the 1860s were developed in detail in Helmholtz's three-component theory of color.

If any pigments are absent in the retinal photoreceptors, then the person does not feel the corresponding tones, i.e. becomes partially color blind. Such was the English physicist Dalton, after whom this visual impairment was named. And it was discovered by none other than Jung at Dalton's.

The phenomenon, called the Purkine effect, after the famous Czech biologist who studied it, indicates that different environments of the eye have different refractions, and this explains the occurrence of some visual illusions.

Optical spectra of atoms or ions are not only a rich source of information about the structure of the atom, they also contain information about the characteristics of the atomic nucleus, primarily related to its electric charge.

Geometric optics is an extremely simple case of optics. Basically, it is a simplified version of wave optics that does not consider and simply does not assume such phenomena as interference and diffraction. Everything here is simplified to the limit. And this is good.

Basic concepts

Geometric optics- the section of optics, which deals with the laws of light propagation in transparent media, the laws of light reflection from mirror surfaces, the principles of constructing images when light passes through optical systems.

Important! All these processes are considered without taking into account the wave properties of light!

In life, geometric optics, being an extremely simplified model, nevertheless finds wide application. It's like classical mechanics and the theory of relativity. It is often much easier to make the required calculation within the framework of classical mechanics.

The basic concept of geometric optics is light beam.

Note that a real light beam does not propagate along the line, but has a finite angular distribution, which depends on the transverse size of the beam. Geometric optics neglects the transverse dimensions of the beam.

The law of rectilinear light propagation

This law tells us that in a homogeneous medium, light propagates in a straight line. In other words, from point A to point B, the light moves along the path that requires the minimum time to overcome.

The law of independence of light rays

The light rays propagate independently of each other. What does it mean? This means that geometric optics assumes that the rays do not affect each other. And they spread as if there were no other rays at all.

Light reflection law

When light meets a specular (reflective) surface, reflection occurs, that is, a change in the direction of propagation of the light beam. So, the law of reflection says that the incident and reflected rays lie in the same plane together with the normal drawn to the point of incidence. Moreover, the angle of incidence is equal to the angle of reflection, i.e. the normal divides the angle between the rays into two equal parts.

Refraction Law (Snell's)

At the interface between the media, along with reflection, refraction also occurs, i.e. the beam is divided into reflected and refracted.

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The ratio of the sines of the angles of incidence and refraction is a constant value and is equal to the ratio of the refractive indices of these media. This value is also called the refractive index of the second medium relative to the first.

Here it is worth considering separately the case of total internal reflection. When light propagates from an optically denser medium to a less dense medium, the angle of refraction is greater in magnitude than the angle of incidence. Accordingly, with an increase in the angle of incidence, the angle of refraction will also increase. At a certain limiting angle of incidence, the angle of refraction will become equal to 90 degrees. With a further increase in the angle of incidence, the light will not be refracted into the second medium, and the intensity of the incident and reflected rays will be equal. This is called total internal reflection.

The law of reversibility of light rays

Let's imagine that a ray, propagating in some direction, has undergone a number of changes and refractions. The law of reversibility of light rays says that if you send another ray towards this ray, then it will follow the same path as the first, but in the opposite direction.

We will continue to study the basics of geometric optics, and in the future we will definitely look at examples of solving problems using various laws. Well, if now you have any questions, welcome to the experts for correct answers. student service... We will help you solve any problem!

Amangeldinov Mustafa Rakhatovich
Student
Nazarbayev Intellectual School mustafastu[email protected] gmail. com

Optics. History of optics. Applications of optics.

The history of the development of optics.

Optics - the study of the nature of light, light phenomena and the interaction of light with matter. And almost all of her story is a story of searching for an answer: what is light?

In the same years, the following facts were discovered:

– straightness of light propagation;

– the phenomenon of light reflection and the law of reflection;

– the phenomenon of light refraction;

– focusing action of a concave mirror.

The ancient Greeks laid the foundation for the branch of optics, which later received the name geometric.

During the Renaissance, many different discoveries and inventions were made; the experimental method began to establish itself as the basis for the study and knowledge of the surrounding world.

On the basis of numerous experimental facts in the middle of the 17th century, two hypotheses arose about the nature of light phenomena:

– corpuscular, which assumed that light is a stream of particles ejected at high speed by luminous bodies;

– wave, which asserted that light is a longitudinal vibrational motion of a special luminiferous medium - ether - excited by vibrations of particles of a luminous body.

All further development of the theory of light up to the present day is the history of the development and struggle of these hypotheses, the authors of which were I. Newton and H. Huygens.

The main provisions of Newton's corpuscular theory:

2) Light corpuscles have different sizes. The largest particles, entering the eye, give the impression of a red color, the smallest - violet.

3) White is a mixture of all colors: red, orange, yellow, green, light blue, blue, purple.

4) Reflection of light from the surface occurs due to the reflection of corpuscles from the wall according to the law of absolute elastic impact.

7) Newton outlined ways of explaining birefringence, hypothesizing that the rays of light have "different sides" - a special property that determines their different refraction when passing through a birefringent body.

Views on the nature of light in the XIX-XX centuries.

In 1801, T. Jung performed an experiment that amazed the world's scientists: S - light source; E - screen; B and C are very narrow slits spaced 1-2 mm apart.

The main provisions of the Fresnel wave theory.

– Light is the propagation of vibrations in the ether at a speed, where the modulus of elasticity of the ether, r is the density of the ether;

– Light waves are transverse;

– The light ether has the properties of an elastic-solid body, it is absolutely incompressible.

When passing from one medium to another, the elasticity of the ether does not change, but its density changes. The relative refractive index of the substance.

Lateral vibrations can occur simultaneously in all directions perpendicular to the direction of wave propagation.

Fresnel's work won the recognition of scientists. Soon a whole series of experimental and theoretical works appeared, confirming the wave nature of light.

– light emission is discrete;

– absorption also occurs in discrete portions, quanta.

The energy of each quantum is represented by the formulaE = hn , whereh Is Planck's constant, and n is the frequency of light.

Five years after Planck, the work of the German physicist Einstein on the photoelectric effect came out. Einstein believed:

– light that has not yet entered into interaction with matter has a granular structure;

– the structural element of discrete light radiation is a photon.

In 1913 the Danish physicist N. Bohr published the theory of the atom, in which he combined the theory of Planck-Einstein quanta with the picture of the nuclear structure of the atom.

Thus, a new quantum theory of light appeared, which was born on the basis of Newton's corpuscular theory. A quantum acts as a corpuscle.

Basic provisions.

– Light is emitted, distributed and absorbed in discrete portions - quanta.

– Quantum of light - a photon carries energy proportional to the frequency of the wave with which it is described by the electromagnetic theoryE = hn .

– Photon, has mass (), momentum and angular momentum ().

– A photon, as a particle, exists only in motion, the speed of which is the speed of propagation of light in a given medium.

– For all interactions in which a photon participates, the general laws of conservation of energy and momentum are valid.

– An electron in an atom can only be in certain discrete stable stationary states. While in stationary states, the atom does not radiate energy.

– When passing from one stationary state to another, an atom emits (absorbs) a photon with a frequency, (whereE 1 andE 2 - energies of the initial and final states).

The achievements of recent years in the field of optics have become possible thanks to the development of both quantum physics and wave optics. The theory of light continues to evolve today.

Wave properties of light and geometric optics.

Optics is a branch of physics that studies the properties and physical nature of light, as well as its interaction with matter.

The concept of a light beam can be obtained from the consideration of a real light beam in a homogeneous medium, from which a narrow parallel beam is extracted with the help of a diaphragm. The smaller the diameter of these holes, the narrower the emitted beam, and in the limit, passing to holes as small as you like, one would see the light beam as a straight line. But such a process of extracting an arbitrarily narrow beam (ray) is impossible due to the phenomenon of diffraction. The inevitable angular expansion of a real light beam transmitted through a diaphragm of diameter D is determined by the diffraction angle j~ l / D ... Only in the limiting case, when l = 0, such an expansion would not take place, and one could speak of a ray as a geometric line, the direction of which determines the direction of propagation of light energy.

Thus, a light ray is an abstract mathematical concept, and geometrical optics is an approximate limiting case into which wave optics goes when the length of a light wave tends to zero.

The eye as an optical system.

The human organ of vision is the eyes, which in many respects represent a very perfect optical system.

Thus, "aiming at the focus" of the human eye is carried out by changing the optical power of the lens with the help of the annular muscle.The ability of the optical system of the eye to create clear images of objects at different distances from it is called accommodation (from the Latin "accommodation" - device). When looking at very distant objects, parallel rays fall into the eye. In this case, the eye is said to be accommodated to infinity.

The convergence of the visual axes of the eyes at a certain point is called convergence. When objects are located at a considerable distance from a person, then when moving the eyes from one object to another between the axes of the eyes, it practically does not change, and the person loses the ability to correctly determine the position of the object. When objects are very far away, the axes of the eyes are parallel, and the person cannot even determine whether the object is moving or not, at which he is looking. The force of the annular muscle, which compresses the lens when examining objects located near a person, also plays a role in determining the position of the bodies.

Spectroscope.

A spectroscope is used to observe the spectra.

The most common prismatic spectroscope consists of two tubes, between which a triangular prism is placed.

Optical measuring device.

Of the devices, projectors for measuring and controlling parts with a complex contour and small dimensions were the first to spread.

The second most common instrument is a universal measuring microscope, in which the part to be measured moves on a longitudinal carriage, and the head microscope - on a transverse one.

Optical measuring instruments are also widely used in geodesy (level, theodolite, etc.).

Theodolite is a geodetic instrument for determining directions and measuring horizontal and vertical angles in geodetic works, topographic and mine surveying, in construction, etc.

Level - a geodetic tool for measuring the elevations of points on the earth's surface - leveling, as well as for setting horizontal directions during assembly, etc. works.

A promising direction in the development of new types of optical measuring devices is equipping them with electronic reading devices, which make it possible to simplify the reading and sighting, etc.

Conclusion.

Bibliography. Artsybyshev S.A. Physics - M .: Medgiz, 1950.

Zhdanov L.S. Zhdanov G.L. Physics for secondary educational institutions - Moscow: Nauka, 1981.

Landsberg G.S. Optics - Moscow: Nauka, 1976.

Landsberg G.S. Elementary physics textbook. - M .: Nauka, 1986.

A.M. Prokhorov Great Soviet Encyclopedia. - M .: Soviet Encyclopedia, 1974.

Sivukhin D.V. General course of physics: Optics - Moscow: Nauka, 1980.