Harmonic vibrations.

Oscillations are processes that differ in varying degrees of repeatability. Oscillatory motion and the waves it causes are very common in nature and technology. Bridges vibrate under the influence of trains passing over them, the eardrum of the ear vibrates, parts of buildings vibrate, and the heart muscle contracts rhythmically.

Depending on the physical nature of the repeating process, vibrations are distinguished: mechanical, electromagnetic, etc. We will consider mechanical vibrations.

Let's consider the simplest mechanical system, consisting of a body (ball) of some mass m, strung on a rod, and a spring with stiffness k, connecting it to a fixed wall. Let us direct the OX axis along the rod, and the origin of coordinates is compatible with the center of the ball, provided that the spring is in an undeformed state. Let's move the ball to a distance X 0 from the equilibrium position (see Fig. 1). Then, from the side of the spring, the body will be affected by elastic force F=-kX 0 (1). This force, as can be seen from equation (1), is proportional to the displacement and is directed in the direction opposite to the displacement. It is called the restoring force. In addition, the system will have a reserve potential energy
. If you release the load, then under the action of elastic force it will begin to move towards the equilibrium position, while its potential energy will decrease, turning into kinetic energy
, the restoring force will decrease and in the equilibrium position will become equal to zero, but the body will not stop in the equilibrium position, but will continue to move by inertia. Its kinetic energy will transform into potential energy, the restoring force will begin to increase, but its direction will change to the opposite. Oscillations will occur in the system. During oscillatory movement, the position of the body at each this moment time is characterized by a distance from the equilibrium position, which is called displacement. Among various types vibrations, the simplest form is harmonic vibration, i.e. one in which the oscillating quantity changes depending on time according to the law of sine or cosine.

1. Undamped harmonic oscillations.

Let a body of mass m be acted upon by a force that tends to return it to the equilibrium position (restoring force) and is proportional to the displacement from the equilibrium position, i.e. elastic force F UPR = -kX. If there is no friction, then the equation of Newton's second law for the body is:

;
or
.

Let's denote
, we get
. (1)

Equation (1) is a linear homogeneous differential equation of the 2nd order, with constant coefficients. The solution to equation (1) will be the law of free or proper damped oscillations:

,

where A is the value of the largest deviation from the equilibrium position, which is called amplitude (amplitude is a constant, positive value);
- oscillation phase; - initial phase.

G graphically undamped oscillations are presented in Fig. 2:

T – period of oscillation (time interval of one complete oscillation);
, Where - circular or cyclic frequency,
, ν is called the oscillation frequency.

To find the speed of a material point during harmonic oscillation, you need to take the derivative of the expression for the displacement:

Where
- maximum speed (speed amplitude). Differentiating this expression, we find the acceleration:

Where
- maximum acceleration.

1. Damped harmonic oscillations.

In real conditions, in addition to the restoring force in the oscillating system, there will be a friction force (medium resistance force), which at low speeds is proportional to the speed of the body:
, where r is the resistance coefficient. If we limit ourselves to taking into account the restoring force and the friction force, then the equation of motion will take the form:
or
, dividing by m, we get:
, denoting
,
, we get:
. This equation is called a second-order linear homogeneous differential equation with constant coefficients. The solution to this equation will be the law of free damped oscillations, and will have the following form: .

From the equation it is clear that the amplitude
is not constant, but depends on time and decreases according to an exponential law. As for undamped oscillations, the value ω is called the circular frequency:
, Where
- attenuation coefficient;

-initial phase.

Graphically damped oscillations are presented in Fig. 3.

ABOUT let's limit the oscillation period
or
, which shows that oscillations in the system can only occur if the resistance is insignificant
. The oscillation period is almost equal
.

With increasing damping coefficient, the oscillation period increases and at
turns to infinity. The movement ceases to be periodic. A system removed from an equilibrium position returns to an equilibrium state without oscillating. This kind of motion is called aperiodic.

Figure 4 shows one of the cases of the system returning to the equilibrium position during aperiodic motion. In accordance with the indicated curve, the charge on the membranes of human nerve fibers decreases.

To characterize the rate of attenuation of oscillations, the concept of attenuation coefficient is introduced
. Let us find the time τ during which the amplitude of oscillations will decrease by a factor of ve:

, i.e.

from where βτ=1, therefore . The attenuation coefficient is the inverse in magnitude of the time period during which the amplitude will decrease by a factor of ve. The ratio of amplitude values ​​corresponding to moments of time differing by a period is equal to
is called the damping decrement, and its logarithm is called the logarithmic damping decrement:

.

Lecture 12. Mechanical vibrations and waves.

Lecture outline

Harmonic oscillations and their characteristics.

Free undamped mechanical vibrations.

Free damped and forced mechanical vibrations.

Elastic waves.

Harmonic oscillations and their characteristics.

Oscillations processes that are characterized by a certain repeatability over time are called, i.e. fluctuations - periodic changes of any size.

Depending on the physical nature, mechanical and electromagnetic vibrations are distinguished. Depending on the nature of the influence on the oscillating system, free (or natural) oscillations are distinguished, forced oscillations, self-oscillations and parametric oscillations.

Oscillations are called periodic if the values ​​of all physical quantities that change when the system oscillates repeat at equal intervals of time.

Period- this is the time it takes to complete one complete oscillation:

Where
- number of oscillations per time .

Oscillation frequency- the number of complete oscillations completed per unit of time.

Cyclic or circular frequency - the number of complete oscillations completed in a time of 2 (time units):

.

The simplest type of oscillations are harmonic vibrations, in which the change in value occurs according to the law of sine or cosine (Fig. 1):

,

Where - the value of the changing quantity;

- amplitude of oscillations, maximum value of the changing quantity;

- phase of oscillations at the moment of time (angular time measure);

 0 - initial phase, determines the value V starting moment time at
,.

An oscillatory system that performs harmonic oscillations is called harmonic oscillator.

Velocity and acceleration during harmonic vibrations:

Free undamped mechanical vibrations.

Free or own are called the oscillations that a system makes around an equilibrium position after it has somehow been removed from a state of stable equilibrium and presented to itself.

As soon as a body (or system) is removed from an equilibrium position, a force immediately appears that tends to return the body to an equilibrium position. This force is called returning, it is always directed towards the equilibrium position, its origin is different:

and for spring pendulum- elastic force;

b) for a mathematical pendulum - the component force of gravity.

Free or natural vibrations are vibrations that occur under the influence of a restoring force.

If there are no friction forces in the system, the oscillations continue indefinitely with a constant amplitude and are called natural undamped oscillations.

Spring pendulum- material point with mass m, suspended on an absolutely elastic weightless spring and oscillating under the action of an elastic force.

Let us consider the dynamics of the natural undamped oscillations of a spring pendulum.

According to Newton's II law,

according to Hooke's law,

Where k– rigidity,
;

or
.

Let's denote cyclic frequency of natural oscillations.

-differential equation free undamped oscillations.

The solution to this equation is the expression: .

period of oscillation of a spring pendulum.

At harmonic vibrations the total energy of the system remains constant, a continuous transition occurs V and vice versa.

Math pendulum- material point, suspended on a weightless inextensible thread (Fig. 2).

It can be proven that in this case

Spring and mathematical pendulums are harmonic oscillators (as are oscillatory circuit). A harmonic oscillator is a system described by the equation:

.

The oscillations of a harmonic oscillator are important example periodic motion and serve as an approximate model in many problems of classical and quantum physics.

Free damped and forced mechanical vibrations.

In every real system, performing mechanical oscillations, there are always certain resistance forces acting (friction at the point of suspension, environmental resistance, etc.), to overcome which the system expends energy, as a result of which real free mechanical oscillations are always damped.

Damped oscillations- These are oscillations whose amplitude decreases with time.

Let's find the law of amplitude change.

For a spring pendulum of mass m, performing small oscillations under the action of an elastic force
The friction force is proportional to the speed:

where r is the resistance coefficient of the medium; the minus sign means that
always directed opposite to the speed.

According to Newton's II law, the equation of motion of a pendulum has the form:

Let's denote:

differential equation of free damped oscillations.

The solution to this equation is the expression:

,

Where cyclic frequency of free damped oscillations,

 0 - cyclic frequency of free undamped oscillations,

 - attenuation coefficient,

A 0 - amplitude at the initial moment of time (t=0).

- law of decreasing amplitude.

Over time, the amplitude decreases according to exponential law(Fig. 3).

Relaxation time is the time during which the amplitude decreases in once.

.

Thus, is the reciprocal of the relaxation time.

The most important characteristic of damped oscillations is the logarithmic damping decrement .

Logarithmic damping decrement is the natural logarithm of the ratio of two amplitudes that differ from each other in time by a period:

.

Let's find out its physical meaning.

Z and the relaxation time the system will have time to complete N oscillations:

those. - this is the quantity reciprocal of a number oscillations, during which the amplitude decreases by a factor of e.

To characterize an oscillatory system, the concept of quality factor is used:

.

Quality factor- physical quantity proportional to the number of oscillations during which the amplitude decreases by e times (Fig. 4,
).

Forced are called oscillations that occur in a system under the influence of periodically changing external force.

Let the external force change according to the harmonic law:

In addition to the external force, a restoring force and a resistance force, proportional to the oscillation speed, act on the oscillating system:

Forced oscillations occur at a frequency equal frequency compelling force. It has been experimentally established that the displacement lags behind the compelling force in its change. It can be proven that

Where - amplitude of forced oscillations,

- oscillation phase difference And
,

;
.

Graphically forced oscillations are presented in Fig. 5.

E If the driving force changes according to a harmonic law, then the vibrations themselves will be harmonic. Their frequency is equal to the frequency of the driving force, and their amplitude is proportional to the amplitude of the driving force.

Dependence of amplitude on driving force frequency leads to the fact that at a certain frequency determined for a given system, the amplitude reaches a maximum.

Phenomenon sharp increase the amplitude of forced oscillations when the frequency of the driving force approaches the natural frequency of the system (the resonant frequency) is called resonance(Fig. 6).

Elastic waves.

Any elastic body consists of a large number of particles (atoms, molecules) interacting with each other. Interaction forces appear when the distance between particles changes (attraction occurs during stretching, and repulsion during compression) and are of an electromagnetic nature. If any particle is removed from its equilibrium position by an external influence, then it will pull another particle along with it in the same direction, this second will pull a third, and the disturbance will propagate from particle to particle in the medium at a certain speed, depending on the properties of the medium. If the particle was shifted upward, then under the action of the upper particles, repulsive, and the lower, attractive, it will begin to move down, pass the equilibrium position, move down by inertia, etc., i.e. will perform harmonic oscillatory motion, forcing a neighboring particle to oscillate, etc. Therefore, when a disturbance propagates in a medium, all particles oscillate with the same frequency, each near its equilibrium position.

The process of propagation of mechanical vibrations in elastic medium called an elastic wave. This process is periodic in time and space. When a wave propagates, the particles of the medium do not move with the wave, but oscillate around their equilibrium positions. Together with the wave, only the state of oscillatory motion and its energy are transferred from particle to particle of the medium. Therefore, the main property of all waves is the transfer of energy without transfer of matter.

There are longitudinal and transverse elastic waves.

An elastic wave is called longitudinal if the particles of the medium oscillate along the direction of propagation of the wave (Fig. 7).

For relative position oscillating points are characterized by condensation and rarefaction.

When such a wave propagates through the medium, condensations and rarefaction occur. Longitudinal waves arise in solid, liquid and gaseous bodies, in which elastic deformations occur during compression or tension.

An elastic wave is called transverse if the particles of the medium oscillate perpendicular to the direction of propagation of the wave (Fig. 8).

P When a transverse wave propagates in an elastic medium, crests and troughs are formed. A transverse wave is possible in a medium where shear deformation causes elastic forces, i.e. V solids. At the interface between 2 liquids or a liquid and a gas, waves appear on the surface of the liquid; they are caused either by tension forces or gravity forces.

Thus, only longitudinal waves, in solids - longitudinal and transverse.

The speed of wave propagation depends on elastic properties environment and its density. The speed of propagation of longitudinal waves is 1.5 times greater than the speed of transverse waves.

Propagating from one source, both waves arrive at the receiver at different times. By measuring the difference in the propagation times of longitudinal and transverse waves, it is possible to determine the location of the wave source ( atomic explosion, earthquake epicenter, etc.).

On the other hand, the speed of wave propagation in earth's crust depends on the rocks lying between the source and receiver of the waves. This is the basis of geophysical methods for studying the composition of the earth's crust and searching for minerals.

Longitudinal waves propagating in gases, liquids and solids and perceived by humans are called sound waves. Their frequency ranges from 16 to 20,000 Hz, below 16 Hz - infrasound, above 20,000 Hz - ultrasound.

Sokolov S.Ya., corresponding member of the USSR Academy of Sciences, in 1927-28. discovered the ability of ultrasonic waves to penetrate metals and developed a technique for ultrasonic flaw detection, constructing the first ultrasonic generator at 10 9 Hz. In 1945, he was the first to develop a method for converting mechanical waves into visible light and created an ultrasonic microscope.

The wave, spreading from the source of oscillations, covers more and more new areas of space.

The geometric location of the points to which the oscillations have propagated at a given time t is called wave front.

The geometric location of points oscillating in the same phase is called wave surface.

There are an infinite number of wave surfaces that can be drawn, but their appearance is the same for a given wave. A wave front represents a wave surface at a given time.

Basically wave surfaces can be of any shape, and in the simplest case it is a set of parallel planes or concentric spheres (Fig. 9).

The wave is called flat, if its front is a plane.

IN the wave is called spherical, if its front is the surface of a sphere.

IN Waves propagating in a homogeneous isotropic medium from point sources are spherical. At a large distance from the source, a spherical wave can be considered as a plane wave.

Huygens' principle: each point of the wave front (i.e., each oscillating particle of the medium) is a source of secondary spherical waves. The new position of the wave front is represented by the envelope of these secondary waves.

This statement was made in 1690 by the Dutch scientist Huygens. Its validity can be illustrated with the help of waves on the surface of water, which imitate spherical waves arising in the volume of an elastic medium.

and 1 in 1 - front at moment t 1,

and 2 in 2 - front at moment t 2.

Having blocked the surface of the water with an obstacle with a small hole and directed a plane wave at the obstacle, we are convinced that behind the obstacle - spherical wave(Fig. 10).

Running are called waves that transfer energy in space.

Let us obtain the equation of a traveling plane wave, assuming that the oscillations are harmonic in nature, and the Y-axis coincides with the direction of wave propagation.

The wave equation determines the dependence of the displacement of an oscillating particle of the medium on coordinates and time.

Let some particle of the medium IN(Fig. 11) is located at a distance at from the vibration source located at the point ABOUT. At the point ABOUT the displacement of a particle of the medium from the equilibrium position occurs according to a harmonic law,

Where t- time counted from the beginning of oscillations.

At the point CWhere
- time during which the wave leaves the point O gets to the point C, - wave propagation speed.

-plane traveling wave equation.

This equation determines the amount of displacement X oscillating point characterized by coordinate at, at any time t.

If a plane wave propagates not in the positive direction of the Y axis, but in opposite direction, That

Because the wave equation can be written as

The distance between nearby points oscillating in the same phase is called the wavelength.

Wavelength- the distance over which the wave propagates during the period of oscillation of the particles of the medium, i.e.

.

Because

where is the wave number.

IN general case
.

Free vibrations always damp due to energy losses (friction, medium resistance, conductor resistance electric current and so on.). Meanwhile, both in technology and in physical experiments There is an urgent need for undamped oscillations, the periodicity of which remains the same as long as the system oscillates at all. How are such vibrations obtained? We know that forced oscillations, in which energy losses are replenished by the work of a periodic external force, are undamped. But where does the external periodic force come from? After all, it, in turn, requires a source of some kind of undamped oscillations.

Undamped oscillations are created by devices that themselves can maintain their oscillations due to some constant source of energy. Such devices are called self-oscillating systems.

In Fig. 55 shows an example of an electromechanical device of this kind. The weight hangs on a spring, the lower end of which is immersed in a cup of mercury when this spring pendulum oscillates. One pole of the battery is connected to the spring at the top, and the other to the cup of mercury. When lowering the load electrical circuit closes and current flows through the spring. Spring coils thanks to magnetic field The currents begin to attract each other, the spring is compressed, and the load receives an upward push. Then the contact is broken, the coils stop tightening, the load falls down again, and the whole process is repeated again.

Thus, the oscillation of the spring pendulum, which would die out on its own, is maintained by periodic shocks caused by the oscillation of the pendulum itself. With each push, the battery releases a portion of energy, part of which is used to lift the load. The system itself controls the force acting on it and regulates the flow of energy from the source - the battery. The oscillations do not die out precisely because during each period just as much energy is taken from the battery as is spent during the same time on friction and other losses. As for the period of these undamped oscillations, it practically coincides with the period of natural oscillations of the load on the spring, i.e., it is determined by the stiffness of the spring and the mass of the load.

Rice. 55. Self-oscillations of a load on a spring

In a similar way, undamped oscillations of a hammer occur in an electric bell, with the only difference being that in it periodic shocks are created by a separate electromagnet that attracts an armature mounted on the hammer. In a similar way, one can obtain self-oscillations with sound frequencies, for example, excite undamped oscillations of a tuning fork (Fig. 56). When the legs of the tuning fork move apart, contact 1 closes; current passes through the winding of electromagnet 2, and the electromagnet tightens the legs of the tuning fork. In this case, the contact opens, and then the entire cycle is repeated.

Rice. 56. Self-oscillations of a tuning fork

The phase difference between the oscillation and the force that it regulates is extremely important for the occurrence of oscillations. Let's move contact 1 from outside tuning fork legs on the inside. The closure now occurs not when the legs diverge, but when the legs come closer, i.e., the moment when the electromagnet is turned on is advanced by half a period compared to the previous experiment. It is easy to see that in this case the tuning fork will be compressed all the time by a continuously switched on electromagnet, i.e., oscillations will not occur at all.

Electromechanical self-oscillating systems are used very widely in technology, but purely mechanical self-oscillating devices are no less common and important. It is enough to point to any clock mechanism. The undamped oscillations of a pendulum or a clock balancer are supported by the potential energy of a raised weight or by the elastic energy of a wound spring.

Figure 57 illustrates the principle of operation of the Galileo-Huygens pendulum clock (§ 11). This figure shows the so-called anchor passage. A wheel with oblique teeth 1 (running wheel) is rigidly attached to a toothed drum, through which a chain with a weight 2 is thrown. A crossbar 4 (anchor) is attached to the pendulum 3, at the ends of which pallets 5 are fixed - plates curved in a circle with the center on the axis of the pendulum 6. The anchor does not allow the running wheel to rotate freely, but gives it the opportunity to rotate only one tooth for every half-period of the pendulum. But the running wheel also acts on the pendulum, namely, while the tooth of the running wheel is in contact with curved surface left or right pallet, the pendulum receives no push and is only slightly slowed down due to friction. But in those moments when the tooth of the running wheel “strikes” along the end of the pallet, the pendulum receives a push in the direction of its movement. Thus, the pendulum makes undamped oscillations, because in certain positions it itself allows the running wheel to push itself into in the right direction. These shocks replenish the energy spent on friction. The period of oscillations in this case almost coincides with the period of natural oscillations of the pendulum, i.e., depends on its length.

Rice. 57. Clock mechanism diagram

Self-oscillations are also vibrations of the string under the action of the bow (in contrast to free vibrations strings of a piano, harp, guitar and other non-bowed string instruments excited by a single push or jerk); self-oscillations are the sound of wind instruments musical instruments, the movement of the piston of a steam engine and many other periodic processes.

A characteristic feature of self-oscillations is that their amplitude is determined by the properties of the system itself, and not by the initial deflection or push, as in free oscillations. If, for example, the pendulum of a clock is deflected too much, then the friction losses will be greater than the energy input from the winding mechanism, and the amplitude will decrease. On the contrary, if the amplitude is reduced, then the excess energy imparted to the pendulum by the running wheel will cause the amplitude to increase. The amplitude at which energy consumption and supply are balanced will be automatically established.

Radiation, radioactivity and radio emission are concepts that even sound quite dangerous. In this article you will learn why some substances are radioactive and what that means. Why is everyone so afraid of radiation and how dangerous is it? Where can we find radioactive substances and what does this threaten us with?

Radioactivity concept

By radioactivity I mean the “ability” of atoms of certain isotopes to split and thereby create radiation. The term “radioactivity” did not appear immediately. Initially, such radiation was called Becquerel rays, in honor of the scientist who discovered it while working with an isotope of uranium. We now call this process the term “ radioactive radiation».

In this rather complex process, the original atom is transformed into an atom of a completely different one. chemical element. Due to the ejection of alpha or beta particles, the mass number of the atom changes and, accordingly, this moves it along D.I. Mendeleev’s table. It is worth noting that the mass number changes, but the mass itself remains almost the same.

Relying on this information, we can rephrase the definition of the concept a little. So, radioactivity is also the ability of unstable atomic nuclei to independently transform into other, more stable and stable nuclei.

Substances - what are they?

Before we talk about what radioactive substances are, let's generally define what is called a substance. So, first of all, it is a type of matter. It is also logical that this matter consists of particles, and in our case these are most often electrons, protons and neutrons. Here we can already talk about atoms, which consist of protons and neutrons. Well, molecules, ions, crystals, and so on are made from atoms.

The concept of a chemical substance is based on the same principles. If it is impossible to isolate a nucleus in matter, then it cannot be classified as a chemical substance.

About radioactive substances

As mentioned above, in order to exhibit radioactivity, an atom must spontaneously decay and turn into an atom of a completely different chemical element. If all the atoms of a substance are unstable enough to decay in this way, then you have a radioactive substance. More technical language the definition would sound like this: substances are radioactive if they contain radionuclides, and in high concentrations.

Where are radioactive substances located in D.I. Mendeleev’s table?

Quite simple and easy way to find out whether a substance is radioactive is to look at D.I. Mendeleev’s table. Everything that comes after the lead element are radioactive elements, as well as promethium and technetium. It is important to remember which substances are radioactive, because it can save your life.

There are also a number of elements that have at least one radioactive isotope in their natural mixtures. Here is a partial list of them, showing some of the most common elements:

• Potassium.
• Calcium.
• Vanadium.
• Germanium.
• Selenium.
• Rubidium.
• Zirconium.
• Molybdenum.
• Cadmium.
• Indium.

Radioactive substances include those that contain any radioactive isotopes.

Types of radioactive radiation

There are several types of radioactive radiation, which will be discussed now. Alpha and beta radiation have already been mentioned, but this is not the entire list.

Alpha radiation is the weakest radiation and is dangerous if particles enter directly into the human body. Such radiation is produced by heavy particles, and that is why it is easily stopped even by a sheet of paper. For the same reason, alpha rays do not travel more than 5 cm.

Beta radiation is stronger than the previous one. This is radiation from electrons, which are much lighter than alpha particles, so they can penetrate several centimeters into human skin.

Gamma radiation is realized by photons, which quite easily penetrate even further to internal organs person.

The most powerful radiation in terms of penetration is neutron radiation. It is quite difficult to hide from it, but in fact it does not exist in nature, except perhaps in close proximity to nuclear reactors.

Impact of radiation on humans

Radioactive hazardous substances can often be fatal to humans. In addition, radiation exposure has an irreversible effect. If you are exposed to radiation, you are doomed. Depending on the extent of the damage, a person dies within a few hours or over many months.

At the same time, it must be said that people are continuously exposed to radioactive radiation. Thank God it's weak enough to have death. For example, by looking Soccer game on television, you get 1 microrad of radiation. Up to 0.2 rad per year is generally the natural radiation background of our planet. 3rd gift - your portion of radiation during dental x-rays. Well, exposure to more than 100 rads is already potentially dangerous.

Harmful radioactive substances, examples and warnings

The most dangerous radioactive substance is Polonium-210. Due to the radiation around it, you can even see a kind of glowing “aura” blue color. It is worth saying that there is a stereotype that all radioactive substances glow. This is not at all true, although there are such variants as Polonium-210. Most radioactive substances are not at all suspicious in appearance.

Livermorium is currently considered the most radioactive metal. Its isotope Livermorium-293 takes 61 milliseconds to decay. This was discovered back in 2000. Ununpentium is slightly inferior to it. The decay time of Ununpentia-289 is 87 milliseconds.

Also interesting fact is that the same substance can be both harmless (if its isotope is stable) and radioactive (if the nuclei of its isotope are about to collapse).

Scientists who studied radioactivity

Radioactive substances for a long time were not considered dangerous, and therefore were freely studied. Unfortunately, sad deaths have taught us that we need to be careful with such substances and increased level security.

One of the first, as already mentioned, was Antoine Becquerel. This is great French physicist, to whom belongs the fame of the discoverer of radioactivity. For his services he was awarded membership in the London royal society. Because of his contributions to this field, he died quite young, at the age of 55. But his work is remembered to this day. The unit of radioactivity itself, as well as craters on the Moon and Mars, were named in his honor.

No less great a person was Marie Skłodowska-Curie, who worked with radioactive substances together with her husband Pierre Curie. Maria was also French, albeit with Polish roots. In addition to physics, she was engaged in teaching and even active social activities. Marie Curie - first woman laureate Nobel Prize in two disciplines at once: physics and chemistry. The discovery of radioactive elements such as Radium and Polonium is the merit of Marie and Pierre Curie.

Conclusion

As we see, radioactivity is quite difficult process, which does not always remain under human control. This is one of those cases where people can find themselves completely powerless in the face of danger. This is why it is important to remember that truly dangerous things can be very deceptive in appearance.

You can most often find out whether a substance is radioactive or not once it has been exposed to it. Therefore, be careful and attentive. Radioactive reactions help us in many ways, but we should also not forget that this is a force practically beyond our control.

In addition, it is worth remembering the contribution of great scientists to the study of radioactivity. They gave us an incredible amount useful knowledge, which now save lives, provide entire countries with energy and help treat terrible diseases. Radioactive chemicals are a danger and a blessing to humanity.

We are all exposed to radiation in one form or another every day. However, in twenty-five places, which we will tell you about below, the level of radiation is much higher, which is why they are included in the list of the 25 most radioactive places on the ground. If you decide to visit any of these places, don't be mad if you later discover an extra pair of eyes when you look in the mirror...(well, maybe that's an exaggeration...or maybe not).

25. Loot alkaline earth metals| Karunagappally, India

Karunagappalli is a municipality in Kollam district. Indian state Kerala, where rare metals are mined. Some of these metals, especially monazite, have become beach sand and alluvial sediments due to erosion. Thanks to this, radiation in some places on the beach reaches 70 mGy/year.

24. Fort d'Aubervilliers | Paris, France


Radiation tests found quite strong radiation at Fort D'Aubervilliers. Cesium-137 and radium-226 were found in 61 of the tanks stored there. In addition, 60 cubic meters its territories were also contaminated with radiation.

23. Acerinox Scrap Metal Processing Plant | Los Barrios, Spain


In this case, the source of cesium-137 was undetected by monitoring devices at the Acherinox scrap metal yard. When the source melted, it released a radioactive cloud with radiation levels up to 1,000 times normal. Contamination was later reported in Germany, France, Italy, Switzerland and Austria.

22. NASA Santa Susana Field Laboratory | Simi Valley, California


The town of Simi Valley, California, is home to NASA's Santa Susanna Field Laboratory, and over the years, problems have been detected at approximately ten nuclear reactors low power due to several fires involving radioactive metals. Cleanup operations are currently underway at this heavily contaminated site.

21. Mayak plutonium production plant | Muslimovo, Soviet Union


Because of the Mayak plutonium extraction plant, built in 1948, residents of Muslimovo in the south Ural mountains suffer from the consequences of using drinking water, contaminated with radiation, which led to chronic diseases and physical disabilities.

20. Church Rock Uranium Mill | Church Rock, New Mexico


During the infamous Church Rock uranium enrichment plant accident, more than a thousand tons of radioactive solid waste and 352,043 cubic meters of acid radioactive waste solution spilled into the Puerco River. As a result, radiation levels increased to 7,000 times normal. A study carried out in 2003 showed that the river's waters are still polluted.

19. Apartment | Kramatorsk, Ukraine


In 1989, a small capsule containing highly radioactive cesium-137 was discovered inside the concrete wall of a residential building in Kramatorsk, Ukraine. The surface of this capsule had a dose of gamma radiation equal to 1800 R/year. As a result, six people died and 17 were injured.

18. Brick houses | Yangjiang, China


The urban district of Yangjiang is replete with houses made of sand and clay bricks. Unfortunately, the sand in this region comes from parts of the hills that contain monazite, which breaks down into radium, actinium and radon. The high level of radiation of these elements explains high rate cancer incidence in the area.

17. Natural background radiation | Ramsar, Iran


This part of Iran has one of the highest levels of natural background radiation on the ground. Radiation levels at Ramsar reach 250 millisieverts per year.

16. Radioactive sand | Guarapari, Brazil


Due to erosion of natural radioactive element The monazite sands of Guarapari's beaches are radioactive, with radiation levels reaching 175 millisieverts, a far cry from the acceptable level of 20 millisieverts.

15. McClure Radioactive Site | Scarborough, Ontario


The McClure radioactive site, a housing development in Scarborough, Ontario, has been a radiation-contaminated site since the 1940s. The contamination was caused by radium recovered from scrap metal that was to be used for experiments.

14. Underground springs Subterranean Springs of Paralana | Arkaroola, Australia


The underground springs of Paralana flow through rocks rich in uranium and, according to research, these hot springs have been bringing radioactive radon and uranium to the surface for more than a billion years.

13. Institute of Radiotherapy of Goiás (Instituto Goiano de Radioterapia) | Goias, Brazil


Radioactive contamination of Goiás, Brazil resulted from radioactive radiation accident after stealing a radiation therapy source from an abandoned hospital. Hundreds of thousands of people have died due to the pollution, and even today radiation is still rampant in several areas of Goiás.

12. Federal Center Denver Federal Center | Denver, Colorado


The Denver Federal Center has been used as a disposal site for a variety of waste, including chemical substances, contaminated materials and road demolition debris. This waste was transported to various locations, resulting in radioactive contamination of several areas in Denver.

11. Base air force McGuire Air Force Base) | Burlington County, New Jersey


In 2007, McGuire Air Force Base was designated by the United States Environmental Protection Agency as Environmental Protection Agency) one of the most polluted air bases in the country. That same year, the US military ordered a cleanup of contaminants at the base, but contamination is still present there.

10. Hanford Nuclear Reservation Site | Hanford, Washington


An integral part of the American atomic bomb project, the Hanford complex produced plutonium for the atomic bomb that was eventually dropped on Nagasaki, Japan. Although the plutonium stockpile was written off, approximately two-thirds of the volume remained at Hanford, causing groundwater contamination.

9. In the middle of the sea | Mediterranean Sea


It is believed that the syndicate controlled Italian mafia, is using the Mediterranean Sea as a dumping ground for hazardous radioactive waste. It is believed that about 40 ships carrying toxic and radioactive waste are sailing through the Mediterranean Sea, leaving a large number of radioactive waste in the oceans.

8. Coast of Somalia | Mogadishu, Somalia


Some claim that the soil of Somalia's unprotected coastline has been used by the mafia to dump nuclear waste and toxic metals, which includes 600 barrels of toxic materials. This, unfortunately, turned out to be true when a tsunami hit the coast in 2004 and rusting barrels buried here several decades ago were discovered.

7. Production Association"Mayak" | Mayak, Russia


The lighthouse in Russia was for many decades the site of a huge nuclear power plant. It all started in 1957, when approximately 100 tons of radioactive waste were released into environment during a disaster that led to an explosion that contaminated a huge area. However, nothing was reported about this explosion until 1980, when it was discovered that since the 50s, radioactive waste from the power plant had been dumped at surrounding area, including Lake Karachay. The contamination exposed more than 400,000 people to high levels of radiation.

6. Sellafield Power Plant | Sellafield, UK


Before it was converted into a commercial site, Sellafield in the UK was used to produce plutonium for atomic bombs. Today, about two thirds of the buildings that are located in Sellafield are considered radioactively contaminated. This facility releases about eight million liters of contaminated waste every day, polluting the environment and causing deaths for people living nearby.

5. Siberian chemical plant| Siberia, Russia


Just like Mayak, Siberia is also home to one of the largest chemical plants in the world. Siberian Chemical Plant produces 125,000 tons solid waste polluting groundwater surrounding area. The study also found that wind and rain carry this waste to wildlife, calling high levels mortality among wild animals.

4. Polygon | Semipalatinsk test site, Kazakhstan


The test site in Kazakhstan is best known for its atomic bomb project. This desolate place was converted into a facility where the Soviet Union blew up its first atomic bomb. The landfill currently holds the record for the largest concentration nuclear explosions in the world. Approximately 200 thousand people are currently suffering from the effects of this radiation.

3. Western mining and chemical plant| Mailuu-Suu, Kyrgyzstan


Mailuu-Suu is considered one of the most polluted places in the world. Unlike other radioactive places, this place does not receive its radiation from nuclear bombs or power plants, but from large-scale uranium mining and processing activities, releasing approximately 1.96 million cubic meters of radioactive waste in the area.

2. Chernobyl Nuclear Power Plant | Chernobyl, Ukraine


Heavily contaminated with radiation, Chernobyl is the site of one of the world's worst nuclear accidents. For many years radiation disaster at Chernobyl affects six million people in the area and is predicted to result in an estimated 4,000 to 93,000 deaths. Nuclear disaster Chernobyl released 100 times more radiation into the atmosphere than was released as a result of the explosion of nuclear bombs in Nagasaki and Hiroshima.

1. Nuclear power plant Fukushima Daini Nuclear Power Plant | Fukushima, Japan


The effects of the earthquake in Fukushima Prefecture in Japan are said to be the longest lasting yet nuclear danger in the world. This disaster, considered the worst nuclear accident after Chernobyl disaster, caused the meltdown of three reactors, which led to a large radiation leak that was discovered 322 kilometers from the power plant.