Corpuscular radiations - ionizing radiation consisting of particles with a mass different from zero.
Alpha radiation - a stream of positively charged particles (nuclei of helium atoms - 24He), which moves at a speed of about 20,000 km/s. Alpha rays are formed during the radioactive decay of the nuclei of elements with large atomic numbers and during nuclear reactions and transformations. Their energy ranges from 4-9 (2-11) MeV. The range of a-particles in a substance depends on their energy and on the nature of the substance in which they move. On average, the distance in air is 2-10 cm, in biological tissue - several microns. Since a-particles are massive and have relatively high energy, their path through matter is straightforward , they cause a strong ionization effect. Specific ionization is approximately 40,000 ion pairs per 1 cm of travel in air (up to 250 thousand ion pairs can be created over the entire travel length). In biological tissue, up to 40,000 ion pairs are also created along a path of 1-2 microns. All energy is transferred to the cells of the body, causing great harm to it.
Alpha particles are trapped by a sheet of paper and are practically unable to penetrate the outer (outer) layer of the skin; they are absorbed by the stratum corneum of the skin. Therefore, a-radiation does not pose a danger until radioactive substances emitting a-particles enter the body through an open wound, with food or inhaled air - then they become extremely dangerous .
Beta radiation - a stream of b-particles consisting of electrons (negatively charged particles) and positrons (positively charged particles) emitted by atomic nuclei during their b-decay. The mass of beta particles in absolute terms is 9.1x10-28 g. Beta particles carry one elementary electric charge and propagate in the medium at a speed of 100 thousand km/s to 300 thousand km/s (i.e. up to the speed light) depending on the radiation energy. The energy of b-particles varies widely. This is explained by the fact that during each b-decay of radioactive nuclei, the resulting energy is distributed between the daughter nucleus, b-particles and neutrinos in different proportions, and the energy of b-particles can fluctuate from zero to some maximum value. The maximum energy ranges from 0.015-0.05 MeV (soft radiation) to 3-13.5 MeV (hard radiation).
Since b-particles have a charge, under the influence of electric and magnetic fields they deviate from the rectilinear direction. Having a very small mass, b-particles, when colliding with atoms and molecules, also easily deviate from their original direction (i.e., they are strongly scattered). Therefore, it is very difficult to determine the path length of beta particles - this path is too tortuous. Mileage
b-particles, due to the fact that they have different amounts of energy, also undergo vibrations. The length of the run in the air can reach
25 cm, and sometimes several meters. In biological tissues, the path of particles is up to 1 cm. The path of motion is also affected by the density of the medium.
The ionizing ability of beta particles is significantly lower than that of alpha particles. The degree of ionization depends on the speed: less speed - more ionization. At 1 cm of travel distance in air, a b-particle forms
50-100 ion pairs (1000-25 thousand ion pairs all the way through the air). High-energy beta particles, flying past the nucleus too quickly, do not have time to cause the same strong ionizing effect as slow beta particles. When energy is lost, it is captured either by a positive ion to form a neutral atom, or by an atom to form a negative ion.
Neutron radiation - radiation consisting of neutrons, i.e. neutral particles. Neutrons are formed during nuclear reactions (a chain reaction of fission of nuclei of heavy radioactive elements, during reactions of synthesis of heavier elements from hydrogen nuclei). Neutron radiation is indirectly ionizable; the formation of ions occurs not under the influence of neutrons themselves, but under the influence of secondary heavy charged particles and gamma quanta, to which the neutrons transfer their energy. Neutron radiation is extremely dangerous due to its high penetrating ability (the range in the air can reach several thousand meters). In addition, neutrons can cause induced radiation (including in living organisms), turning atoms of stable elements into their radioactive ones. Hydrogen-containing materials (graphite, paraffin, water, etc.) are well protected from neutron irradiation.
Depending on the energy, the following neutrons are distinguished:
1. Ultrafast neutrons with an energy of 10-50 MeV. They are formed during nuclear explosions and the operation of nuclear reactors.
2. Fast neutrons, their energy exceeds 100 keV.
3. Intermediate neutrons - their energy is from 100 keV to 1 keV.
4. Slow and thermal neutrons. The energy of slow neutrons does not exceed 1 keV. The energy of thermal neutrons reaches 0.025 eV.
Neutron radiation is used for neutron therapy in medicine, determining the content of individual elements and their isotopes in biological media, etc. Medical radiology uses mainly fast and thermal neutrons, mainly using californium-252, which decays to release neutrons with an average energy of 2.3 MeV.
Electromagnetic radiation differ in their origin, energy, and wavelength. Electromagnetic radiation includes x-rays, gamma radiation from radioactive elements, and bremsstrahlung, which occurs when highly accelerated charged particles pass through matter. Visible light and radio waves are also electromagnetic radiation, but they do not ionize matter, because they are characterized by a long wavelength (less rigidity). The energy of the electromagnetic field is not emitted continuously, but in separate portions - quanta (photons). Therefore, electromagnetic radiation is a stream of quanta or photons.
X-ray radiation. X-rays were discovered by Wilhelm Conrad Roentgen in 1895. X-rays are quantum electromagnetic radiation with a wavelength of 0.001-10 nm. Radiation with a wavelength exceeding 0.2 nm is conventionally called “soft” X-ray radiation, and up to 0.2 nm - “hard”. Wavelength is the distance over which radiation travels during one oscillation period. X-ray radiation, like any electromagnetic radiation, travels at the speed of light - 300,000 km/s. The X-ray energy usually does not exceed 500 keV.
There are bremsstrahlung and characteristic X-rays. Bremsstrahlung radiation occurs when fast electrons are decelerated in the electrostatic field of atomic nuclei (i.e., when electrons interact with atomic nuclei). When a high-energy electron passes near the nucleus, scattering (deceleration) of the electron is observed. The speed of the electron decreases, and part of its energy is emitted in the form of a bremsstrahlung X-ray photon.
Characteristic X-rays arise when fast electrons penetrate deep into an atom and are knocked out of internal levels (K, L and even M). The atom is excited and then returns to the ground state. In this case, electrons from the external levels fill the vacated spaces in the internal levels and at the same time photons of characteristic radiation are emitted with an energy equal to the difference in the energy of the atom in the excited and ground states (not exceeding 250 keV). Those. characteristic radiation occurs when the electronic shells of atoms are rearranged. During various transitions of atoms from an excited state to a non-excited state, excess energy can also be emitted in the form of visible light, infrared and ultraviolet rays. Since X-rays have short wavelengths and are less absorbed in matter, they have greater penetrating power.
Gamma radiation - This is radiation of nuclear origin. It is emitted by atomic nuclei during the alpha and beta decay of natural artificial radionuclides in cases where the daughter nucleus contains excess energy that is not captured by corpuscular radiation (alpha and beta particles). This excess energy is instantly emitted in the form of gamma rays. Those. Gamma radiation is a stream of electromagnetic waves (quanta) that is emitted during the process of radioactive decay when the energy state of nuclei changes. In addition, gamma quanta are formed during the antihilation of a positron and an electron. The properties of gamma radiation are close to x-rays, but have greater speed and energy. The speed of propagation in a vacuum is equal to the speed of light - 300,000 km/s. Since gamma rays have no charge, they are not deflected in electric and magnetic fields, propagating straight and evenly in all directions from the source. The energy of gamma radiation ranges from tens of thousands to millions of electron volts (2-3 MeV), rarely reaching 5-6 MeV (the average energy of gamma rays produced during the decay of cobalt-60 is 1.25 MeV). The gamma radiation flux includes quanta of various energies. When decaying 131
In 1896 Becquerel discovered the phenomenon of radioactivity.
Becquerel discovered that the chemical element uranium spontaneously (i.e., without any external influences) emits previously unknown invisible rays, which were later called radioactive radiation.
The ability of atoms of some chemical elements to spontaneously emit is called radioactivity.
In 1899, as a result of the experiment of Ernest Rutherford, it was discovered that radioactive radiation has a complex composition. Rutherford took a thick-walled lead vessel with a grain of radium at the bottom. A beam of radioactive radiation from radium exited through a narrow hole and fell on a photographic plate. After developing the photographic plate, one dark spot was discovered on it - exactly in the place where the beam hit. If we carry out the same experiment, creating a strong magnetic field acting on the beam, then three spots appear on the developed plate: one central, two others - on opposite sides of the central one. In one stream there were only positively charged particles, in the other - negatively charged ones. And the central flow was radiation that had no electrical charge.
Positively charged particles were called alpha particles (α-particles), negatively charged ones were called beta particles (β-particles), and neutral ones were called gamma particles (γ-particles) or gamma quanta.
Some time later, as a result of studying various physical characteristics and properties of these particles (electric charge, mass, etc.), it was possible to establish that the α particle is the nucleus of a helium atom (); A β particle is an electron (), and a γ particle is an energy quantum. The appearance of an electron inside the nucleus is explained by the decay of a neutron into a proton and an electron.
Radioactive radiation often leads to changes in the structure of the nucleus:
α-radiation: ,
β-radiation: ,
γ-radiation: .
The number preceding the letter designation of the core at the top is called mass number, and below - charge number(or atomic number).
The mass number of the nucleus of an atom of a given chemical element, accurate to whole numbers, is equal to the number of atomic mass units contained in the mass of this nucleus and is equal to the number of particles in the nucleus.
The charge number of the nucleus of an atom of a given chemical element is equal to the number of elementary electrical charges contained in the charge of this nucleus, and is equal to the number of protons in the nucleus.
During the process of radioactive decay, the laws of conservation of mass number and charge are satisfied.
Radioactive radiation has a strong effect on matter, especially living cells. Their effect depends on the type of radiation. With external irradiation, the most dangerous is γ - radiation, because it has the greatest penetrating ability. During internal irradiation, α-radiation is the most dangerous, because these particles cause the greatest degree of ionization of cells. Even relatively weak radiation, which, when completely absorbed, increases body temperature by only 0.001ºC, disrupts the vital activity of cells.
Therefore, when working with radiation sources, it is necessary to use various protective measures:
1. Accounting for time and radiation dose.
2. Use of protective equipment.
So, to attenuate α-radiation by half, a sheet of paper is enough, β-radiation - a layer of aluminum 1-5 mm thick, γ-radiation - a sheet of lead, 1-2 cm thick.
Ticket number 24. Rutherford's experiments. Planetary model of the atom. Composition of the atomic nucleus. Nuclear reactions.
In 1903 Thomson proposed a model of the structure of the atom in which all positive charge is uniformly distributed throughout the volume of the atom. In 1911, Rutherford conducted an experiment, the results of which refuted Thomson's theory. For his experiments, Rutherford used a lead vessel with a radioactive substance emitting α particles. From this vessel, alpha particles fly out through a narrow channel.
Since α-particles cannot be directly seen, a glass screen coated with a thin layer of a special substance is used to detect them, due to which flashes occur in places where α-particles hit the screen, which are observed using a microscope. This entire installation is placed in a vessel from which the air has been evacuated (to eliminate the scattering of α-particles due to their collisions with air molecules).
If there are no obstacles in the path of α-particles, then they fall onto the screen in a narrow, slightly expanding beam. If a thin foil made of the metal under study is placed in the path of the α-particles, then when interacting with the substance, the α-particles are scattered in all directions at different angles β. A certain number of particles were scattered at angles close to 90°, and single particles were scattered at angles of the order of 180°. Rutherford came to the conclusion that such a strong deflection of α particles is possible only if inside the atom the positive charge is concentrated in a very small volume (compared to the volume of the atom).
Based on these experiments, Rutherford suggested that at the center of the atom there is a positively charged atomic nucleus. At a great distance from it (compared to its size) there are electrons in the atom. They are attracted, but do not come close to the nucleus, because they move quickly around it.
The nucleus contains positively charged protons. Each proton has a mass 1840 times greater than the mass of an electron; the charge of a proton is positive, equal in absolute value to the charge of an electron. In addition to protons, the nuclei of atoms contain neutrons. The mass of a neutron is slightly greater than the mass of a proton, and its charge is zero.
In 1903, Ernest Rutherford and his collaborator, Frederick Soddy, discovered that the radioactive element radium undergoes alpha decay into another chemical element, radon.
Radium and radon are completely different substances; they differ in their physical and chemical properties. Radium is a metal; under normal conditions it is in a solid state, and radon is an inert gas. These chemical elements occupy different cells in D.I. Mendeleev’s table. Their atoms differ in mass, nuclear charge, and the number of electrons in the electron shell. They enter into chemical reactions in different ways.
Further experiments with various radioactive drugs showed that not only during α-decay, but also during β-decay, the transformation of one chemical element into another occurs.
After Rutherford proposed the nuclear model of the atom in 1911, it became obvious that it is the nucleus that undergoes changes during radioactive transformations. If the changes affected only the electron shell of the atom, then the atom would turn into an ion of the same chemical element, and not into an atom of another element. A similar situation occurs when nuclei interact with particles or with each other.
Transformations of atomic nuclei caused by their interactions with various particles or with each other are called nuclear reactions.
In the process of nuclear reactions, the laws of conservation of mass number and charge are fulfilled.
Some nuclear reactions occur with the release of energy, others with absorption. An example of nuclear reactions is the uranium fission chain reaction and thermonuclear fusion reactions.
Thus, thanks to the thermonuclear fusion reaction (), the Sun releases a huge amount of energy, which allows life to exist on Earth.
After the discovery of radioactive elements, research began into the physical nature of their radiation. In addition to Becquerel and the Curies, Rutherford took up this task.
The classic experiment that made it possible to detect the complex composition of radioactive radiation was as follows. The radium preparation was placed at the bottom of a narrow channel in a piece of lead. There was a photographic plate opposite the channel. The radiation emerging from the channel was affected by a strong magnetic field, the induction lines of which were perpendicular to the beam (Fig. 13.6). The entire installation was placed in a vacuum.
In the absence of a magnetic field, one dark spot was detected on the photographic plate after development exactly opposite the channel. In a magnetic field, the beam split into three beams. The two components of the primary flow were deflected in opposite directions. This indicated that these radiations had electrical charges of opposite signs. In this case, the negative component of the radiation was deflected by the magnetic field much more strongly than the positive one. The third component was not deflected by the magnetic field at all. The positively charged component is called alpha rays, the negatively charged component is called beta rays, and the neutral component is called gamma rays (α-rays, β-rays, γ-rays).
These three types of radiation differ greatly in penetrating ability, that is, in how intensely they are absorbed by various substances. α-rays have the least penetrating power. A layer of paper about 0.1 mm thick is already opaque for them. If you cover a hole in a lead plate with a piece of paper, then no spot corresponding to a-radiation will be found on the photographic plate.
Much less β-rays are absorbed when passing through matter. The aluminum plate completely stops them only with a thickness of a few millimeters. γ-rays have the greatest penetrating ability.
The intensity of absorption of γ-rays increases with increasing atomic number of the absorbing substance. But a layer of lead 1 cm thick is not an insurmountable obstacle for them. When y-rays pass through such a layer of lead, their intensity weakens only by half.
The physical nature of α-, β- and γ-rays is obviously different.
Gamma rays. In their properties, γ-rays are very similar to X-rays, but their penetrating power is much greater than that of X-rays. This suggested that gamma rays were electromagnetic waves. All doubts about this disappeared after the diffraction of γ-rays on crystals was discovered and their wavelength was measured. It turned out to be very small - from 10 -8 to 10 -11 cm.
On the scale of electromagnetic waves, γ rays directly follow X-rays. The propagation speed of γ-rays is the same as that of all electromagnetic waves - about 300,000 km/s.
Beta rays. From the very beginning, α- and β-rays were considered as streams of charged particles. It was easiest to experiment with β-rays, since they are more strongly deflected in both magnetic and electric fields.
The main task of the experimenters was to determine the charge and mass of the particles. When studying the deflection of β-particles in electric and magnetic fields, it was found that they are nothing more than electrons moving at speeds very close to the speed of light. It is important that the velocities of β-particles emitted by any radioactive element are not the same. There are particles with very different speeds. This leads to expansion of the beam of β-particles in a magnetic field (see Fig. 13.6).
It was more difficult to find out the nature of α-particles, since they are less strongly deflected by magnetic and electric fields. Rutherford finally succeeded in solving this problem. He measured the ratio of a particle's charge q to its mass m by its deflection in a magnetic field. It turned out to be approximately 2 times less than that of a proton - the nucleus of a hydrogen atom. The charge of a proton is equal to the elementary one, and its mass is very close to the atomic mass unit 1 . Consequently, an α particle has a mass per elementary charge equal to two atomic mass units.
1 An atomic mass unit (amu) is equal to 1/12 the mass of a carbon atom; 1 a. e.m. ≈ 1.66057 10 -27 kg.
But the charge of the α particle and its mass remained, nevertheless, unknown. It was necessary to measure either the charge or the mass of the α particle. With the advent of the Geiger counter, it became possible to measure charge more easily and accurately. Through a very thin window, alpha particles can penetrate into the counter and be registered by it.
Rutherford placed a Geiger counter in the path of the alpha particles, which measured the number of particles emitted by a radioactive drug over a certain time. Then he replaced the counter with a metal cylinder connected to a sensitive electrometer (Fig. 13.7). Using an electrometer, Rutherford measured the charge of α-particles emitted by the source into the cylinder in the same time (the radioactivity of many substances remains almost unchanged with time). Knowing the total charge of α-particles and their number, Rutherford determined the ratio of these quantities, i.e., the charge of one α-particle. This charge turned out to be equal to two elementary ones.
Thus, he established that an α particle has two atomic mass units for each of its two elementary charges. Therefore, there are four atomic mass units per two elementary charges. The helium nucleus has the same charge and the same relative atomic mass. It follows from this that the α particle is the nucleus of a helium atom.
Not content with the achieved result, Rutherford then proved through direct experiments that it is helium that is formed during radioactive a-decay. Collecting α-particles inside a special tank for several days, he, using spectral analysis, was convinced that helium was accumulating in the vessel (each α-particle captured two electrons and turned into a helium atom).
Radioactive decay produces α-rays (nuclei of the helium atom), β-rays (electrons), and γ-rays (short-wave electromagnetic radiation).
Question for the paragraph
Why did it turn out to be much more difficult to determine the nature of α-rays than in the case of β-rays?
It's no secret that radiation is harmful. Everyone knows this. Everyone has heard about the terrible casualties and the dangers of radioactive exposure. What is radiation? How does it arise? Are there different types of radiation? And how to protect yourself from it?
The word "radiation" comes from the Latin radius and denotes a ray. In principle, radiation is all types of radiation existing in nature - radio waves, visible light, ultraviolet and so on. But there are different types of radiation, some of them are useful, some are harmful. In ordinary life, we are accustomed to using the word radiation to refer to harmful radiation resulting from the radioactivity of certain types of substances. Let's look at how the phenomenon of radioactivity is explained in physics lessons.
Radioactivity in physics
We know that atoms of matter consist of a nucleus and electrons rotating around it. So the core is, in principle, a very stable formation that is difficult to destroy. However, the atomic nuclei of some substances are unstable and can emit various energies and particles into space.
This radiation is called radioactive, and it includes several components, which are named according to the first three letters of the Greek alphabet: α-, β- and γ- radiation. (alpha, beta and gamma radiation). These radiations are different, and their effect on humans and measures to protect against it are also different. Let's look at everything in order.
Alpha radiation
Alpha radiation is a stream of heavy, positively charged particles. Occurs as a result of the decay of atoms of heavy elements such as uranium, radium and thorium. In the air, alpha radiation travels no more than five centimeters and, as a rule, is completely blocked by a sheet of paper or the outer dead layer of skin. However, if a substance that emits alpha particles enters the body through food or air, it irradiates internal organs and becomes dangerous.
Beta radiation
Beta radiation is electrons that are much smaller than alpha particles and can penetrate several centimeters deep into the body. You can protect yourself from it with a thin sheet of metal, window glass, and even ordinary clothing. When beta radiation reaches unprotected areas of the body, it usually affects the upper layers of the skin. During the Chernobyl nuclear power plant accident in 1986, firefighters suffered skin burns as a result of very strong exposure to beta particles. If a substance that emits beta particles enters the body, it will irradiate internal tissues.
Gamma radiation
Gamma radiation is photons, i.e. electromagnetic wave carrying energy. In the air it can travel long distances, gradually losing energy as a result of collisions with atoms of the medium. Intense gamma radiation, if not protected from it, can damage not only the skin, but also internal tissues. Dense and heavy materials such as iron and lead are excellent barriers to gamma radiation.
As you can see, according to its characteristics, alpha radiation is practically not dangerous if you do not inhale its particles or eat them with food. Beta radiation can cause skin burns due to exposure. Gamma radiation has the most dangerous properties. It penetrates deep into the body, and it is very difficult to remove it from there, and the effects are very destructive.
In any case, without special instruments, it is impossible to know what type of radiation is present in this particular case, especially since you can always accidentally inhale radiation particles in the air. Therefore, there is only one general rule - to avoid such places, and if you find yourself, then wrap yourself in as much clothing and things as possible, breathe through the fabric, do not eat or drink, and try to leave the place of infection as quickly as possible. And then, at the first opportunity, get rid of all these things and wash yourself thoroughly.
The purpose of the lesson: to find out what the phenomenon of radioactivity is, what is the composition, nature and properties of radioactive radiation. To achieve an understanding of the meaning of the physical concept of “radioactive radiation”.
Literature and equipment:
- Myakishev G.Ya. Physics 11 – M.: Education, 2010
- Portrait of M. and P. Curie.
- Periodic table.
- Table “Scale of electromagnetic radiation”.
- Projector.
- Laptop.
- Screen.
Lesson progress
Discovery of more natural radioactivity.
The words “radioactive radiation”, “radioactive elements”, “radiation” are known to everyone today. Many people probably also know that radioactive radiation serves people: in some cases they make it possible to make the correct diagnosis of a disease, and also treat dangerous diseases, increase the yield of cultivated plants, etc.
Controversy.
The phenomenon of radioactivity.
It is this phenomenon that will serve as the object of our conversation today.
What do you know about this phenomenon? What is your attitude towards him?
Controversy Generalization of the obtained data.
What is more: positive or negative from information about this phenomenon?
Negativity.
What do you think is the problem?
Why, despite all the troubles that accompany the phenomenon of radioactivity, do people still widely use it?
I propose to formulate the purpose of our lesson.
The goals and objectives are formulated by schoolchildren.
Purpose: To study the phenomenon of radioactivity and its significance for humans.
Now let’s formulate the tasks that serve as stages of our work.
1) Consider the concept of radioactivity.
2) Consider the types of radioactivity.
3) Familiarize yourself with the areas of application of radioactivity.
4) Determine the value of radioactivity for humans.
Solving the problem.
To solve this problem, we will have to solve several problematic problems.
In order to solve our first task - to formulate a definition of the concept of “radioactivity” - we need to think about the meaning of the term itself. Let's try to reveal its etymology. What two bases does this word consist of?
Radio activity
“radiare” – lat. emit rays
Activity speaks for itself.
In what case does a substance, an atom, emit something?
If it falls apart.
Note the second meaning of the Latin word "radiare" - rays.
Radioactivity was discovered by the French scientist Henri Becquerel in 1896. He studied the glow of certain substances, in particular uranium salts (double sulfate of uranium and potassium), previously irradiated with sunlight.
Radioactivity is the spontaneous decay of atomic nuclei with the emission of elementary particles.
Students make messages.
This is how the scientist describes his experiments in his first speech.
Student Report No. 1:
“We wrap a bromogelatin Lumiere photographic plate with two sheets of black paper, very thick, such that the plate is not veiled by exposure to the sun during the day. Place a plate (uranium salt crystal) on a piece of paper outside and expose it all to the sun for several hours. When we then develop the photographic plate, we see that a black silhouette of this plate appears on the negative. If, however, between the plate and the paper we place a coin or a metal screen cut with an openwork pattern, we see an image of these objects appearing on the negative. The crystal plate in question emits rays that pass through paper, opaque to light, and distinguish silver salts.”
Student Report No. 2:
“Among the previous experiments, some were prepared on Wednesday 26 and Thursday 27 February, and since the sun appeared intermittently on those days, I mothballed the experiments, fully prepared, and returned the photographic plates to the dark, in a furniture box, leaving the uranium salt plates in place . In the following days the sun did not appear again. I developed the plates on March 1st, hoping to find faint images. The silhouettes, on the contrary, appeared with great intensity.”
A. Becquerel's father and grandfather studied luminescent substances.
“It was quite clear why the phenomenon of radioactivity was made in our laboratory, and if my father had been alive in 1896. He would be the one to do it.”
A. Becquerel, having discovered a new phenomenon, did not yet know (and could not know) what it was connected with, he only spoke of it as a “new order of phenomena.”
Students conclude: uranium salts spontaneously, without the influence of external factors, create some kind of radiation.
Properties of radioactive radiation. Discovery of radioactive elements.
Intensive studies of radioactive radiation began, with the aim of studying their properties and composition, and also to determine whether other elements emit similar radiation. The first studies were carried out by Becquerel himself, and then by M. Sklodowska-Curie and P. Curie, and Rutherford also did this.
Properties of radioactive radiation:
Act on a photographic plate,
Ionizes the air
Penetrates through thin metal plates
Complete independence from external conditions (lighting, pressure, temperature).
The main efforts in the search for new elements with the ability to spontaneously irradiate were made by M. and P. Curie. they discovered thorium, and then, after processing a huge amount of uranium ore, they isolated new chemical elements, which they called “polonium”, “radium” (radiant) (0.1 g of Radium in 1902)
What can this substance (radium) do?
E. Curie “Marie Curie” (p. 163)
The phenomenon of spontaneous radiation was called radioactivity by the Curies.
It was subsequently established. That all chemical elements with an atomic number greater than 83 are radioactive.
Lighter nuclei also have radioactive isotopes.
Student message “M. Curie’s contribution to the study of radioactivity.”
Physical nature of radioactive radiation.
Radioactive radiation has a complex composition.
Students read the description of the experience (textbook p. 308 Fig. 258) and fill out the table independently.
Properties of radioactive radiation (A.S. Enochovich Handbook of Physics and Technology p. 208 table 260.)
| α-λ teach | β-λ teach | γ-λ teach | |
| The speed of particles emitted from the nuclei of radioactive substances. | 14000–20000 km/s | 160000 km/s | 300000 km/s |
| Particle energy. | 4–9 MeV | from hundredths to 1–2 MeV | 0.2 – 3 MeV |
| The mass of one emitted particle. | 6.6*10 kg | 9*10 kg | 2.2*10 kg |
| Mileage (path traversed by a particle in a substance before stopping): in the air, in aluminum in biological tissue. |
up to several hundred meters, in lead up to 5 cm permeate the human body. |
Radioactivity is the spontaneous, continuous disintegration of some natural and artificial elements, not amenable to any external influence, with the formation of new nuclei, during which these substances emit alpha, beta, and gamma radiation.
Fastening:
In the scientific literature, in newspapers and magazines, the concept of “radioactive radiation” is often found. What is it? What types of radioactive radiation do you know?
V. Mayakovsky “Conversation with the financial inspector about poetry”:
Poetry is like radium mining.
Per gram production,
During the years of labor.
You exhaust one word for the sake of
Thousands of tons of verbal ore.
With the research of which famous scientists can the poet’s work be compared?
Answer in writing the question: “Why, despite all the consequences, does humanity continue to actively use radioactivity?”
Because the significance is great for a person, and the consequences can be avoided with the right approach, use and lifestyle.
Read the famous physicist's words as he considered the results of his experiment of bombarding a sheet of gold with alpha particles. Give the name of the scientist and the year when he drew the conclusion from this experiment.
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