What artistic techniques help the poet convey the emotional. What artistic techniques help the poet convey the emotional state of a lonely traveler in the forest? What melody is created by alternating long and short

Response Plan

1. First postulate. 2. Second postulate. 3. Types of spectra.

Bohr based his theory on two postulates. The first postulate: an atomic system can only be in special stationary or quantum states, each of which has its own energy; In a stationary state, the atom does not radiate.

This means that an electron (for example, in a hydrogen atom) can be in several well-defined orbits. Each electron orbit corresponds to a very specific energy.

Second postulate: during the transition from one stationary state to another, a quantum is emitted or absorbed electromagnetic radiation. The energy of a photon is equal to the difference between the energies of an atom in two states: hv = Е m – Ε n; h = 6.62 10 -34 J s, where h is Planck’s constant.

When an electron moves from a near orbit to a more distant one, the atomic system absorbs a quantum of energy. When an electron moves from a more distant orbit to a closer orbit relative to the nucleus, the atomic system emits an energy quantum.

Bohr's theory made it possible to explain the existence of line spectra.

The emission (or absorption) spectrum is a set of waves of certain frequencies that are emitted (or absorbed) by an atom of a given substance.

Spectra are solid, line and striped.

Continuous spectra emit all substances in a solid or liquid state. The solid spectrum contains waves of all frequencies of visible light and therefore appears as a color band with a smooth transition from one color to another in the following order: Red, Orange, Yellow, Green, Blue and Violet (Every Hunter Wants to Know Where the Pheasant Sits).

Line spectra emit all substances in the atomic state. Atoms of all substances emit sets of waves of very specific frequencies that are unique to them. Just as each person has his own personal fingerprints, so the atom of a given substance has its own spectrum, characteristic only for it. Line emission spectra look like colored lines separated by spaces. The nature of line spectra is explained by the fact that the atoms of a particular substance have only its own stationary states with their own characteristic energy, and therefore their own set of pairs of energy levels that the atom can change, i.e., an electron in an atom can move only from one specific orbits to other, well-defined orbits for a given chemical substance.

Banded spectra are emitted by molecules. Striped spectra look similar to line spectra, only instead of individual lines, separate series of lines are observed, perceived as individual bands.

It is characteristic that whatever spectrum is emitted by these atoms, the same is absorbed, i.e., the emission spectra according to the set of emitted frequencies coincide with the absorption spectra. Since atoms different substances correspond to spectra characteristic only of them, then there is a way to determine chemical composition substances by studying their spectra. This method is called spectral analysis. Spectral analysis is used to determine the chemical composition of fossil ores during mining, to determine the chemical composition of stars, atmospheres, planets; is the main method for monitoring the composition of a substance in metallurgy and mechanical engineering.

Spectrum- distribution of energy emitted or absorbed by a substance across frequencies or wavelengths.

If in the path of the beam sunlight penetrating through a narrow long rectangular slit, place a prism, then on the screen we will see not an image of the slit, but a stretched color strip with a gradual transition of colors from red to violet - a spectrum. This phenomenon was observed by Newton. This means that sunlight contains electromagnetic waves of different frequencies. This spectrum is called solid.

If you pass light emitted by a heated gas through a prism, the spectrum will look like individual colored lines on a black background. This spectrum is called line emission spectrum. This means that the heated gas emits electromagnetic waves with a certain set of frequencies. At the same time, each chemical element emits a characteristic spectrum different from the spectra of other elements.

If light passes through a gas, dark lines appear - line absorption spectrum.

Spectral analysis- a method for determining the qualitative and quantitative composition of a substance, based on obtaining and studying its spectra.

Patterns of atomic radiation

Light emission occurs when an electron in an atom transitions from the highest energy level E k to one of the lower energy levels E n (k > n). The atom in this case emits a photon with energy

Absorption of light is the reverse process. An atom absorbs a photon and moves from a lower state k to a higher state n (n > k). The atom in this case absorbs a photon with energy

This article introduces the basic concepts needed to understand how light is emitted and absorbed by atoms. The application of these phenomena is also described here.

Smartphone and physics

A person who was born after 1990 cannot imagine his life without a variety of electronic devices. The smartphone not only replaces the telephone, but also makes it possible to monitor exchange rates, make transactions, call a taxi and even correspond with astronauts on board the ISS through its applications. Accordingly, all these digital assistants are taken for granted. The emission and absorption of light by atoms, which made possible the era of shrinkage of all kinds of devices, will seem to such readers only a boring topic in physics lessons. But there is a lot of interesting and exciting things in this section of physics.

Theoretical background for the discovery of spectra

There is a saying: “Curiosity will never lead you to any good.” But this expression rather refers to the fact that it is better not to interfere in other people’s relationships. If you show curiosity about the world around you, nothing bad will happen. At the end of the nineteenth century, it became clear to people (it is well described in Maxwell’s system of equations). The next question that scientists wanted to solve was the structure of matter. We must immediately clarify: what is valuable for science is not the emission and absorption of light by atoms. Line spectra are a consequence of this phenomenon and the basis for studying the structure of substances.

Atomic structure

Scientists are still in Ancient Greece suggested that marble consists of some indivisible pieces, “atoms”. And until the end of the nineteenth century, people thought that these were the smallest particles of matter. But Rutherford's experiment on the scattering of heavy particles on gold foil showed: the atom also has internal structure. The heavy nucleus is located in the center and is positively charged; light negative electrons revolve around it.

Paradoxes of the atom within the framework of Maxwell's theory

These data gave rise to several paradoxes: according to Maxwell's equations, any moving charged particle emits an electromagnetic field, and therefore loses energy. Why then do the electrons not fall onto the nucleus, but continue to rotate? It was also not clear why each atom absorbs or emits photons of only a certain wavelength. Bohr's theory made it possible to eliminate these inconsistencies by introducing orbitals. According to the postulates of this theory, electrons can only be around the nucleus in these orbitals. The transition between two neighboring states is accompanied by either the emission or absorption of a quantum with a certain energy. The emission and absorption of light by atoms occurs precisely because of this.

Wavelength, frequency, energy

For a more complete picture, it is necessary to tell a little about photons. This elementary particles, which have no rest mass. They exist only while they move through the medium. But they still have mass: when they hit a surface, they transfer momentum to it, which would be impossible without mass. They simply convert their mass into energy, making the substance they hit and are absorbed by a little warmer. Bohr's theory does not explain this fact. The properties of a photon and the features of its behavior are described by quantum physics. So, a photon is both a wave and a particle with mass. A photon, and like a wave, has the following characteristics: length (λ), frequency (ν), energy (E). How longer length waves, the lower the frequency, and the lower the energy.

Spectrum of an atom

The atomic spectrum is formed in several stages.

An electron in an atom moves from orbital 2 (higher energy) to orbital 1 (lower energy).
A certain amount of energy is released, which is formed as a quantum of light (hν).
radiated into the surrounding space.

This is how a line spectrum of an atom is obtained. Why it is called that way is explained by its shape: when special devices “catch” outgoing photons of light, a series of lines are recorded on the recording device. To separate photons of different wavelengths, the phenomenon of diffraction is used: waves with different frequencies have different indicator refraction, therefore some are deviated more than others.

and spectra

Substances are unique to each type of atom. That is, hydrogen, when emitted, will give one set of lines, and gold - another. This fact is the basis for the use of spectrometry. Having obtained the spectrum of anything, you can understand what the substance consists of and how the atoms in it are located relative to each other. This method allows one to determine various properties of materials, which is often used in chemistry and physics. The absorption and emission of light by atoms is one of the most common tools for studying the world around us.

Disadvantages of the emission spectra method

To at this moment it was rather about how atoms radiate. But usually all electrons are in their orbitals in a state of equilibrium; they have no reason to move to other states. For a substance to emit something, it must first absorb energy. This is a disadvantage of the method, which exploits the absorption and emission of light by an atom. Briefly, a substance must first be heated or illuminated before we obtain a spectrum. No questions will arise if a scientist studies stars; they already glow thanks to their own internal processes. But if you need to study a piece of ore or food product, then to obtain a spectrum it actually needs to be burned. This method is not always suitable.

Absorption spectra

Emission and absorption of light by atoms as a method “works” in two directions. You can shine broadband light on a substance (that is, one in which photons are present different lengths waves), and then see which wavelengths were absorbed. But this method is not always suitable: it is necessary that the substance be transparent for the desired part of the electromagnetic scale.

Qualitative and quantitative analysis

It became clear: the spectra are unique for each substance. The reader could conclude that such analysis is used only to determine what the material is made of. However, the possibilities of the spectra are much wider. Using special techniques for examining and recognizing the width and intensity of the resulting lines, it is possible to determine the number of atoms included in the compound. Moreover, this indicator can be expressed in different units:

as a percentage (for example, this alloy contains 1% aluminum);
in moles (3 moles of table salt are dissolved in this liquid);
in grams (this sample contains 0.2 g of uranium and 0.4 grams of thorium).

Sometimes the analysis is mixed: qualitative and quantitative at the same time. But if earlier physicists memorized the position of lines and assessed their shade using special tables, now all this is done by programs.

Application of spectra

We have already discussed in some detail what the emission and absorption of light by atoms is. Spectral analysis is used very widely. There is no area human activity, wherever the phenomenon we are considering is used. Here are some of them:

At the very beginning of the article we talked about smartphones. Silicon semiconductor elements have become so small thanks in part to studies of crystals using spectral analysis.
In any incident, it is the uniqueness electron shell each atom makes it possible to determine which bullet was fired first, why the frame of a car broke or a tower crane fell, as well as what poison a person was poisoned with and how long he spent in the water.
Medicine used spectral analysis for its purposes most often in relation to body fluids, but it happens that this method is also applied to tissues.
Distant galaxies, clouds of cosmic gas, planets near alien stars - all this is studied with the help of light and its decomposition into spectra. Scientists learn the composition of these objects, their speed and the processes that occur in them by being able to record and analyze the photons they emit or absorb.

Electromagnetic scale

What we pay most attention to is visible light. But on the electromagnetic scale this segment is very small. What the human eye cannot detect is much wider than the seven colors of the rainbow. Not only visible photons (λ = 380-780 nanometers), but also other quanta can be emitted and absorbed. Electromagnetic scale includes:

Radio waves(λ = 100 kilometers) transmit information over long distances. Due to their very long wavelength, their energy is very low. They are very easily absorbed.
Terahertz waves(λ = 1-0.1 millimeters) were difficult to access until recently. Previously, their range was included in radio waves, but now this segment of the electromagnetic scale is allocated to a separate class.
Infrared waves (λ = 0.74-2000 micrometers) transfer heat. A fire, a lamp, the Sun emit them in abundance.

We have considered visible light, so we will not write about it in more detail.

Ultraviolet waves(λ = 10-400 nanometers) are lethal to humans in excess, but their deficiency also causes our central star to produce a lot of ultraviolet radiation, and the Earth’s atmosphere retains most of it.

X-ray and gamma quanta (λ < 10 нанометров) имеют общий диапазон, но различаются по происхождению. Чтобы получить их, нужно разогнать электроны или атомы до очень high speeds. Human laboratories are capable of this, but in nature such energies are found only inside stars or during collisions of massive objects. Examples of the latter process include supernova explosions, the absorption of a star by a black hole, the meeting of two galaxies, or the meeting of a galaxy and a massive cloud of gas.

Electromagnetic waves of all ranges, namely their ability to be emitted and absorbed by atoms, are used in human activity. Regardless of what the reader has chosen (or is just about to choose) as his path in life, he will definitely encounter the results of spectral research. The seller uses a modern payment terminal only because a scientist once studied the properties of substances and created a microchip. The farmer fertilizes the fields and now reaps large harvests only because a geologist once discovered phosphorus in a piece of ore. The girl wears bright clothes only thanks to the invention of permanent chemical dyes.

But if the reader wants to connect his life with the world of science, then he will have to study much more than the basic concepts of the process of emission and absorption of light quanta in atoms.