THE GOVERNMENT OF MOSCOW
DEPARTMENT OF EDUCATION OF THE CITY OF MOSCOW
EASTERN DISTRICT DEPARTMENT
STATE BUDGET EDUCATIONAL INSTITUTION
SECONDARY EDUCATIONAL SCHOOL № 000
111141 Moscow, st. Perovskaya house 44-a, building 1,2 Telephone
Lesson No. 5 (28.02.13)
"Work with text"
Exam materials in physics include tasks that test the ability of students to master new information for them, work with this information, answer questions, the answers to which follow from the text proposed for study. After studying the text, three tasks are offered (No. 16.17 - basic level, No. 18 - advanced level).
Gilbert's experiments on magnetism.
Gilbert cut a ball out of a natural magnet so that it had poles at two diametrically opposite points. He called this spherical magnet terella (Fig. 1), that is, a small Earth. By bringing a moving magnetic needle closer to it, one can clearly show the various positions of the magnetic needle that it takes at various points on the earth's surface: at the equator, the arrow is parallel to the horizon plane, at the pole - perpendicular to the horizon plane.
Let us consider an experiment that reveals "magnetism through influence." We hang two iron strips parallel to each other on threads and we will slowly bring a large permanent magnet to them. In this case, the lower ends of the strips diverge, since they are magnetized in the same way (Fig. 2a). As the magnet approaches further, the lower ends of the strips converge somewhat, since the pole of the magnet itself begins to act on them with greater force (Fig. 2b).
Task 16
How does the angle of inclination of the magnetic needle change as it moves across the globe along the meridian from the equator to the pole?
1) is increasing all the time
2) decreases all the time
3) first increases, then decreases
4) first decreases, then increases
Correct answer: 1
Task 17
At what points are the magnetic poles of the terella located (Fig. 1)?
Correct answer: 2
Task 18
In an experiment that reveals "magnetism through influence", both iron strips are magnetized. Figures 2a and 2b show the poles of the left strip for both cases.
At the lower end of the right strip
1) in both cases, the south pole appears
2) in both cases, the north pole appears
3) in the first case, the northern one arises, and in the second, the southern one arises
4) in the first case, the south arises, and in the second, the north arises
Correct answer: 2
Ptolemy's experiments on the refraction of light.
The Greek astronomer Claudius Ptolemy (circa 130 AD) is the author of a remarkable book that served as the main textbook on astronomy for almost 15 centuries. However, in addition to the astronomical textbook, Ptolemy also wrote the book "Optics", in which he outlined the theory of vision, the theory of flat and spherical mirrors and the study of the phenomenon of light refraction.
Ptolemy encountered the phenomenon of light refraction while observing the stars. He noticed that a beam of light, passing from one medium to another, "breaks". Therefore, a stellar ray, passing through the earth's atmosphere, reaches the surface of the earth not in a straight line, but along a curved line, that is, refraction occurs. The curvature of the beam path occurs due to the fact that the air density changes with height.
To study the law of refraction, Ptolemy conducted the following experiment..gif" width="13" height="24 src="> (see figure). The rulers could rotate around the center of the circle on a common axis O.
Ptolemy immersed this circle in water up to the diameter AB and, turning the lower ruler, ensured that the rulers lay for the eye on one straight line (if you look along the upper ruler). After that, he took the circle out of the water and compared the angles of incidence α and refraction β . He measured angles with an accuracy of 0.5°. The numbers obtained by Ptolemy are presented in the table.
Angle of incidence α , deg | ||||||||
Refraction angle β , deg |
Ptolemy did not find a "formula" for the relationship between these two series of numbers. However, if you determine the sines of these angles, it turns out that the ratio of the sines is expressed by almost the same number, even with such a rough measurement of the angles that Ptolemy resorted to.
Task 16
Refraction in the text refers to the phenomenon
1) changes in the direction of propagation of the light beam due to reflection at the boundary of the atmosphere
2) changes in the direction of propagation of the light beam due to refraction in the Earth's atmosphere
3) absorption of light as it propagates in the Earth's atmosphere
4) rounding of obstacles by a light beam and, thereby, deviations from rectilinear propagation
Correct answer: 2
Task 17
Which of the following conclusions contradicts Ptolemy's experiments?
1) the angle of refraction is less than the angle of incidence when the beam passes from air to water
2) with an increase in the angle of incidence, the angle of refraction increases linearly
3) the ratio of the sine of the angle of incidence to the sine of the angle of refraction does not change
4) the sine of the angle of refraction depends linearly on the sine of the angle of incidence
Correct answer: 2
Task 18
Due to the refraction of light in a calm atmosphere, the apparent position of the stars in the sky relative to the horizon
1) above actual position
2) below actual position
3) shifted in one direction or another vertically relative to the actual position
4) matches the actual position
Correct answer: 1
Thomson's experiments and the discovery of the electron
At the end of the 19th century, many experiments were carried out to study the electric discharge in rarefied gases. The discharge was initiated between a cathode and an anode sealed inside a glass tube from which the air was evacuated. That which passed from the cathode was called cathode rays.
To determine the nature of cathode rays, the English physicist Joseph John Thomson (1856 - 1940) conducted the following experiment. His experimental setup was a vacuum cathode ray tube (see figure). The incandescent cathode K was the source of cathode rays, which were accelerated by the electric field existing between the anode A and the cathode K. There was a hole in the center of the anode. The cathode rays that passed through this hole hit the point G on the wall of the tube S opposite the hole in the anode. If the wall S is covered with a fluorescent substance, then the hit of the rays at point G appears as a luminous spot. On the way from A to G, the beams passed between the plates of the capacitor CD, to which the voltage from the battery could be applied.
If this battery is turned on, then the rays are deflected by the electric field of the capacitor and a spot appears on the screen S in position . Thomson suggested that cathode rays behave like negatively charged particles. By creating in the area between the plates of the capacitor also a uniform magnetic field perpendicular to the plane of the figure (it is shown by dots), it is possible to cause the spot to deviate in the same or the opposite direction.
Experiments have shown that the charge of the particle is equal in absolute value to the charge of the hydrogen ion (C), and its mass is almost 1840 times less than the mass of the hydrogen ion.
In the future, it was called the electron. The day April 30, 1897, when Joseph John Thomson reported on his research, is considered the "birthday" of the electron.
Task 16
What are cathode rays?
1) x-rays
2) gamma rays
3) electron flow
4) ion flow
Correct answer: 3
Task 17
BUT. Cathode rays interact with an electric field.
B. Cathode rays interact with a magnetic field.
1) only A
2) only B
4) neither A nor B
Correct answer: 3
Task 18
Cathode rays (see figure) will hit point G, provided that between the plates of the capacitor CD
1) only the electric field acts
2) only the magnetic field acts
3) the action of forces from the electric and magnetic fields is compensated
4) the action of forces from the magnetic field is negligible
Correct answer: 3
Experimental discovery of the law of equivalence of heat and work.
In 1807, the physicist J. Gay-Lussac, who studied the properties of gases, set up a simple experiment. It has long been known that a compressed gas cools as it expands. Gay-Lussac forced the gas to expand into a void - into a vessel, the air from which was previously pumped out. To his surprise, no decrease in temperature occurred, the temperature of the gas did not change. The researcher could not explain the result: why does the same gas, equally compressed, while expanding, cool if it is released directly into the atmosphere, and does not cool if it is released into an empty vessel, where the pressure is zero?
The German doctor Robert Mayer managed to explain the experience. Mayer had the idea that work and heat can be converted into one another. This remarkable idea immediately enabled Mayer to make clear the mysterious result in the Gay-Lussac experiment: if heat and work are mutually converted, then when the gas expands into a void, when it does not do any work, since there is no force (pressure) opposing its increase volume, gas and should not be cooled. If, when expanding the gas, it has to do work against external pressure, its temperature should decrease. You can't get a job for free! Mayer's remarkable result has been confirmed many times by direct measurements; Of particular importance were the experiments of Joule, who measured the amount of heat needed to heat a liquid with a stirrer rotating in it. At the same time, both the work expended on the rotation of the stirrer and the amount of heat received by the liquid were measured. No matter how the experimental conditions changed, different liquids, different vessels and stirrers were taken, the result was the same: the same amount of heat was always obtained from the same work.
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Melting curve (p - pressure, T - temperature)
According to modern concepts, most of the earth's interior remains solid. However, the substance of the asthenosphere (the Earth's shell from 100 km to 300 km in depth) is in an almost molten state. This is the name of the solid state, which easily turns into a liquid (molten) with a slight increase in temperature (process 1) or a decrease in pressure (process 2).
The source of primary magma melts is the asthenosphere. If pressure decreases in some region (for example, when sections of the lithosphere are displaced), then the solid matter of the asthenosphere immediately turns into a liquid melt, i.e., into magma.
But what physical causes actuate the mechanism of a volcanic eruption?
Along with water vapor, magma contains various gases (carbon dioxide, hydrogen chloride and fluoride, sulfur oxides, methane, and others). The concentration of dissolved gases corresponds to the external pressure. In physics, Henry's law is known: the concentration of a gas dissolved in a liquid is proportional to its pressure over the liquid. Now imagine that the pressure at depth has decreased. Gases dissolved in magma become gaseous. Magma increases in volume, foams and begins to rise up. As the magma rises, the pressure drops even more, so the process of outgassing increases, which, in turn, leads to an acceleration of the rise.
Task 16
In what state of aggregation is the substance of the asthenosphere in regions I and II on the diagram (see figure)?
1) I - in liquid, II - in solid
2) I - in solid, II - in liquid
3) I - in liquid, II - in liquid
4) I - in solid, II - in solid
Correct answer: 2
Task 17
What force causes molten frothy magma to rise up?
1) gravity
2) elastic force
3) the power of Archimedes
4) friction force
Correct answer: 3
Task 18
Decompression sickness is a disease that occurs when a diver rises quickly from a great depth. Decompression sickness occurs in humans with a rapid change in external pressure. When working under conditions of increased pressure, human tissues absorb additional amounts of nitrogen. Therefore, scuba divers must ascend slowly so that the blood has time to carry the resulting gas bubbles into the lungs.
Which statements are true?
BUT. The concentration of nitrogen dissolved in the blood is the greater, the greater the depth of the diver's immersion.
B. With an excessively rapid transition from a high-pressure environment to a low-pressure environment, excess nitrogen dissolved in the tissues is released, forming gas bubbles.
1) only A
2) only B
4) neither A nor B
Correct answer: 3
Geysers
Geysers are located near active or recently dormant volcanoes. Geysers need heat from volcanoes to erupt.
To understand the physics of geysers, recall that the boiling point of water depends on pressure (see figure).
The dependence of the boiling point of water on the pressure
1) will move downward under atmospheric pressure
2) will remain in equilibrium, since its temperature is below the boiling point
3) will quickly cool down, since its temperature is below the boiling point at a depth of 10 m
4) will boil, since its temperature is higher than the boiling point at external pressure Pa
Correct answer: 4
Fog
Under certain conditions, water vapor in the air partially condenses, resulting in water droplets of fog. Water droplets have a diameter of 0.5 µm to 100 µm.
Take a vessel, fill it halfway with water and close the lid. The fastest water molecules, having overcome the attraction from other molecules, jump out of the water and form steam above the surface of the water. This process is called water evaporation. On the other hand, water vapor molecules, colliding with each other and with other air molecules, can randomly end up near the surface of the water and pass back into the liquid. This is steam condensation. In the end, at a given temperature, the processes of evaporation and condensation are mutually compensated, that is, a state of thermodynamic equilibrium is established. Water vapor, which is in this case above the surface of the liquid, is called saturated.
If the temperature is raised, then the evaporation rate increases and equilibrium is established at a higher water vapor density. Thus, the density of saturated vapor increases with increasing temperature (see figure).
The dependence of the density of saturated water vapor on temperature
For fog to occur, it is necessary that the vapor becomes not just saturated, but supersaturated. Water vapor becomes saturated (and supersaturated) with sufficient cooling (AB process) or in the process of additional evaporation of water (AC process). Accordingly, the resulting mist is referred to as cooling mist and evaporation mist.
The second condition necessary for the formation of fog is the presence of nuclei (centers) of condensation. The role of nuclei can be played by ions, the smallest droplets of water, dust particles, soot particles and other small contaminants. The greater the air pollution, the greater the density of fogs.
Task 16
From the graph in the figure, it can be seen that at a temperature of 20 ° C, the density of saturated water vapor is 17.3 g/m3. This means that at 20°C
5) in 1 m the mass of saturated water vapor is 17.3 g
6) in 17.3 m of air there is 1 g of saturated water vapor
8) air density is 17.3 g/m
Correct answer: 1
Task 17
In which process indicated on the graph can evaporation fog be observed?
1) only AB
2) AC only
4) neither AB nor AC
Correct answer: 2
Task 18
Which statements are true?
BUT. Urban fogs are denser than fogs in mountainous areas.
B. Fogs are observed with a sharp increase in air temperature.
1) only A
2) only B
4) neither A nor B
Correct answer: 1
The color of the sky and the setting sun
Why is the sky blue? Why does the setting sun turn red? It turns out that in both cases the reason is the same - the scattering of sunlight in the earth's atmosphere.
In 1869, the English physicist J. Tyndall performed the following experiment: a weakly diverging narrow beam of light passed through a rectangular aquarium filled with water. At the same time, it was noted that if you look at the light beam in the aquarium from the side, it appears bluish. And if you look at the beam from the exit end, then the light acquires a reddish tint. This can be explained by assuming that blue (cyan) light is scattered more than red. Therefore, when a white light beam passes through a scattering medium, blue light is mainly scattered from it, so that red light begins to predominate in the beam leaving the medium. The longer the white beam travels in the scattering medium, the more red it appears at the output.
In 1871, J. Strett (Rayleigh) developed a theory of the scattering of light waves by small particles. The law established by Rayleigh states that the intensity of the scattered light is proportional to the fourth power of the frequency of the light, or, in other words, inversely proportional to the fourth power of the wavelength of the light.
Rayleigh put forward a hypothesis according to which the centers that scatter light are air molecules. Later, already in the first half of the 20th century, it was found that fluctuations in air density play the main role in light scattering - microscopic thickening and rarefaction of air resulting from the chaotic thermal motion of air molecules.
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The disc on which sound is recorded is made of a special soft wax material. A copper copy (cliché) is removed from this wax disc by electroforming. This uses the deposition of pure copper on the electrode when an electric current passes through a solution of its salts. The copper copy is then imprinted on plastic disks. This is how gramophone records are made.
When playing sound, a gramophone record is placed under a needle connected to the membrane of the gramophone, and the record is brought into rotation. Moving along the wavy groove of the plate, the end of the needle vibrates, and the membrane vibrates with it, and these vibrations quite accurately reproduce the recorded sound.
Task 16
What vibrations does the horn membrane make under the action of a sound wave?
5) free
6) damped
7) forced
8) self-oscillations
Correct answer: 3
Task 17
What action of the current is used when obtaining a cliché from a wax disc?
1) magnetic
2) thermal
3) light
4) chemical
Correct answer: 4
Task 18
When recording sound mechanically, a tuning fork is used. With an increase in the sounding time of the tuning fork by 2 times
5) the length of the sound groove will increase by 2 times
6) the length of the sound groove will decrease by 2 times
7) the depth of the sound groove will increase by 2 times
8) the depth of the sound groove will decrease by 2 times
Correct answer: 1
Magnetic suspension
The average speed of trains on railways does not exceed
150 km/h Designing a train that can match the speed of an airplane is not easy. At high speeds, train wheels cannot withstand the load. There is only one way out: to abandon the wheels, making the train fly. One way to "hang" a train over the rails is to use magnet repulsion.
In 1910, the Belgian E. Bachelet built the world's first model of a flying train and tested it. A 50-kilogram cigar-shaped trailer of a flying train accelerated to a speed of over 500 km / h! The Bachelet magnetic road was a chain of metal posts with coils mounted on their tops. After turning on the current, the trailer with built-in magnets was raised above the coils and accelerated by the same magnetic field over which it was suspended.
Almost simultaneously with Bachelet in 1911, Professor of the Tomsk Institute of Technology B. Weinberg developed a much more economical suspension for a flying train. Weinberg proposed not to push the road and the cars away from each other, which is fraught with huge energy costs, but to attract them with ordinary electromagnets. The electromagnets of the road were positioned above the train to compensate for the train's gravity with their attraction. The iron wagon was originally located not exactly under the electromagnet, but behind it. At the same time, electromagnets were mounted along the entire length of the road. When the current in the first electromagnet was turned on, the trailer rose and moved forward, towards the magnet. But a moment before the trailer was supposed to stick to the electromagnet, the current was turned off. The train continued to fly by inertia, lowering its height. The next electromagnet was turned on, the train rose again and accelerated. By placing his car in a copper pipe, from which the air was pumped out, Weinberg dispersed the car to a speed of 800 km / h!
Task 16
Which of the magnetic interactions can be used for magnetic suspension?
BUT. Attraction of opposite poles.
B. Repulsion of like poles.
1) only A
2) only B
3) neither A nor B
Correct answer: 4
Task 17
When a maglev train moves
1) there are no friction forces between the train and the road
2) air resistance forces are negligible
3) electrostatic repulsion forces are used
4) the forces of attraction of the same magnetic poles are used
Correct answer: 1
Task 18
In B. Weinberg's model of a magnetic train, it was necessary to use a wagon with a larger mass. In order for the new trailer to move in the same mode, it is necessary
5) replace the copper pipe with an iron one
6) do not turn off the current in the electromagnets until the trailer "sticks"
7) increase the current strength in electromagnets
8) mount electromagnets along the length of the road at greater intervals
Correct answer: 3
Piezoelectricity
In 1880, the French scientists brothers Pierre and Paul Curie investigated the properties of crystals. They noticed that if a quartz crystal is compressed from two sides, then on its faces perpendicular to the direction of compression, electric charges arise: on one face - positive, on the other - negative. Crystals of tourmaline, Rochelle salt, even sugar have the same property. Charges on the crystal faces also arise when it is stretched. Moreover, if a positive charge accumulated on a face during compression, then a negative charge will accumulate on this face during tension, and vice versa. This phenomenon was called piezoelectricity (from the Greek word "piezo" - I press). A crystal with this property is called a piezoelectric. Later, the Curie brothers discovered that the piezoelectric effect is reversible: if opposite electric charges are created on the faces of a crystal, it will either shrink or stretch, depending on which face a positive and negative charge is applied to.
The action of widespread piezoelectric lighters is based on the phenomenon of piezoelectricity. The main part of such a lighter is a piezoelectric element - a ceramic piezoelectric cylinder with metal electrodes on the bases. With the help of a mechanical device, a short-term impact is made on the piezoelectric element. At the same time, opposite electric charges appear on its two sides, located perpendicular to the direction of action of the deforming force. The voltage between these sides can reach several thousand volts. Through insulated wires, voltage is supplied to two electrodes located in the tip of the lighter at a distance of 3 - 4 mm from each other. A spark discharge between the electrodes ignites the mixture of gas and air.
Despite very high voltages (~ 10 kV), experiments with a piezo lighter are completely safe, since even with a short circuit, the current strength is negligible and safe for human health, as with electrostatic discharges when removing woolen or synthetic clothes in dry weather.
Task 16
Piezoelectricity is a phenomenon
1) the appearance of electric charges on the surface of crystals during their deformation
2) the occurrence of tensile and compressive deformation in crystals
3) the passage of electric current through the crystals
4) passage of a spark discharge during crystal deformation
Correct answer: 1
Task 17
Using a piezo lighter does not represent danger, because
7) the current strength is negligible
8) a current of 1 A is safe for a person
Correct answer: 3
Task 18
At the beginning of the 20th century, the French scientist Paul Langevin invented the emitter of ultrasonic waves. Charging the faces of a quartz crystal with electricity from a high-frequency alternator, he found that the crystal oscillates with the frequency of voltage changes. The emitter is based on
1) direct piezoelectric effect
2) reverse piezoelectric effect
3) the phenomenon of electrification under the action of an external electric field
4) the phenomenon of electrification upon impact
Correct answer: 2
Construction of the Egyptian pyramids
The Pyramid of Cheops is one of the seven wonders of the world. There are still many questions about how exactly the pyramid was built.
It was not easy to transport, lift and install stones, the mass of which was tens and hundreds of tons.
In order to lift the stone blocks up, they came up with a very tricky way. Bulk earthen ramps were erected around the construction site. As the pyramid grew, the ramps rose higher and higher, as if encircling the entire future building. Stones were dragged along the ramp on sleds in the same way as on the ground, while helping themselves with levers. The angle of inclination of the ramp was very slight - 5 or 6 degrees, because of this, the length of the ramp grew to hundreds of meters. So, during the construction of the Khafre pyramid, the ramp connecting the upper temple with the lower one, with a level difference of more than 45 m, had a length of 494 m and a width of 4.5 m.
In 2007, French architect Jean-Pierre Houdin suggested that during the construction of the pyramid of Cheops, ancient Egyptian engineers used a system of both external and internal ramps and tunnels. Houdin believes that only the lower one was built with the help of external ramps,
43-meter part (the total height of the pyramid of Cheops is 146 meters). To lift and install the rest of the blocks, a system of internal ramps arranged in a spiral was used. To do this, the Egyptians dismantled the outer ramps and moved them inside. The architect is sure that the cavities discovered in 1986 in the thickness of the Cheops pyramid are tunnels into which the ramps gradually turned.
Task 16
What type of simple mechanisms does a ramp belong to?
5) movable block
6) fixed block
8) inclined plane
Correct answer: 4
Task 17
The ramps include
5) freight elevator in residential buildings
6) boom crane
7) a gate for raising water from a well
8) an inclined platform for the entry of vehicles
Correct answer: 4
Task 18
If friction is neglected, then the ramp that connected the upper temple with the lower one during the construction of the pyramid of Khafre made it possible to gain
5) The strength is about 11 times
6) Effective more than 100 times
7) in work about 11 times
8) in a distance of about 11 times
Correct answer: 1
Earth Albedo
The temperature near the Earth's surface depends on the reflectivity of the planet - albedo. The surface albedo is the ratio of the energy flux of reflected solar rays to the energy flux of solar rays incident on the surface, expressed as a percentage or fraction of a unit. The Earth's albedo in the visible part of the spectrum is about 40%. In the absence of clouds, it would be about 15%.
Albedo depends on many factors: the presence and condition of cloudiness, changes in glaciers, seasons, and, accordingly, on precipitation. In the 90s of the 20th century, the significant role of aerosols, the smallest solid and liquid particles in the atmosphere, became obvious. When fuel is burned, gaseous oxides of sulfur and nitrogen enter the air; combining in the atmosphere with water droplets, they form sulfuric, nitric acids and ammonia, which then turn into sulfate and nitrate aerosols. Aerosols not only reflect sunlight without letting it through to the Earth's surface. Aerosol particles serve as nuclei for the condensation of atmospheric moisture during the formation of clouds and, thereby, contribute to an increase in cloudiness. And this, in turn, reduces the influx of solar heat to the earth's surface.
Transparency for solar rays in the lower layers of the earth's atmosphere also depends on fires. Due to fires, dust and soot rise into the atmosphere, which cover the Earth with a dense screen and increase the surface albedo.
Task 16
Surface albedo is understood as
1) the total flux of solar rays falling on the Earth's surface
2) the ratio of the energy flux of reflected radiation to the flux of absorbed radiation
3) the ratio of the energy flux of reflected radiation to the flux of incident radiation
4) the difference between the incident and reflected radiation energy
Correct answer: 3
Task 17
Which statements are true?
BUT. Aerosols reflect sunlight and thus contribute to a decrease in the Earth's albedo.
B. Volcanic eruptions contribute to an increase in the Earth's albedo.
1) only A
2) only B
4) neither A nor B
Correct answer: 2
Task 18
The table shows some characteristics for the planets of the solar system - Venus and Mars. It is known that the albedo of Venus is A = 0.76, and the albedo of Mars is A = 0.15. Which of the characteristics mainly influenced the difference in the albedo of the planets?
Characteristics | Venus | Mars |
BUT. Average distance from the Sun, in radii of the Earth's orbit | ||
B. Average radius of the planet, km | ||
AT. Number of satellites | ||
G. Presence of atmosphere | very dense | sparse |
Correct answer: 4
Greenhouse effect
To determine the temperature of an object heated by the Sun, it is important to know its distance from the Sun. The closer a planet in the solar system is to the sun, the higher its average temperature. For an object as far from the Sun as the Earth, a numerical estimate of the average temperature on the surface gives the following result: T Å ≈ –15°C.
In reality, the Earth's climate is much milder. Its average surface temperature is about 18 ° C due to the so-called greenhouse effect - heating the lower part of the atmosphere by radiation from the Earth's surface.
Nitrogen (78%) and oxygen (21%) predominate in the lower layers of the atmosphere. The remaining components account for only 1%. But it is this percentage that determines the optical properties of the atmosphere, since nitrogen and oxygen almost do not interact with radiation.
The effect of the "greenhouse" is known to everyone who has dealt with this uncomplicated garden structure. In the atmosphere it looks like this. Part of the solar radiation, not reflected from the clouds, passes through the atmosphere, which plays the role of glass or film, and heats the earth's surface. The heated surface cools down, emitting thermal radiation, but this is another radiation - infrared. The average wavelength of such radiation is much longer than that coming from the Sun, and therefore the atmosphere, which is almost transparent to visible light, transmits infrared radiation much worse.
Water vapor absorbs about 62% of infrared radiation, which contributes to the heating of the lower atmosphere. Water vapor in the list of greenhouse gases is followed by carbon dioxide (CO2), which absorbs 22% of the Earth's infrared radiation in clear air.
The atmosphere absorbs the flow of long-wave radiation rising from the surface of the planet, heats up and, in turn, heats the surface of the Earth. The maximum in the solar radiation spectrum falls at a wavelength of about 550 nm. The maximum in the spectrum of the Earth's radiation falls on a wavelength of about 10 microns. The role of the greenhouse effect is illustrated in Figure 1.
Fig.1(a). Curve 1 - the calculated spectrum of solar radiation (with a photosphere temperature of 6000°C); curve 2 - calculated radiation spectrum of the Earth (with a surface temperature of 25°C)
Fig.1 (b). Absorption (in percentage terms) by the earth's atmosphere of radiation at different wavelengths. In the region of the spectrum from 10 to 20 μm, there are absorption bands of CO2, H2O, O3, CH4 molecules. They absorb the radiation coming from the Earth's surface.
Task 16
Which gas plays the largest role in the greenhouse effect of the Earth's atmosphere?
10) oxygen
11) carbon dioxide
12) water vapor
Correct answer: 4
Task 17
Which of the following statements correspond to the curve in Figure 1(b)?
BUT. Visible radiation, corresponding to the maximum of the solar spectrum, passes through the atmosphere almost unhindered.
B. Infrared radiation with a wavelength exceeding 10 microns, practically does not pass beyond the earth's atmosphere.
5) only A
6) only B
8) neither A nor B
Correct answer: 3
Task 18
Thanks to the greenhouse effect
1) in cold cloudy weather, woolen clothing protects the human body from hypothermia
2) tea in a thermos stays hot for a long time
3) the sun's rays passing through the glazed windows heat the air in the room
4) on a sunny summer day, the water temperature in reservoirs is lower than the temperature of the sand on the shore
Correct answer: 3
Human hearing
The lowest tone perceived by a person with normal hearing has a frequency of about 20 Hz. The upper limit of auditory perception varies greatly from person to person. Age is of particular importance here. At the age of eighteen, with perfect hearing, you can hear sound up to 20 kHz, but on average, the limits of audibility for any age lie in the range of 18 - 16 kHz. With age, the sensitivity of the human ear to high-frequency sounds gradually decreases. The figure shows a graph of the dependence of the level of perception of sound on frequency for people of different ages.
Soreness" href="/text/category/boleznennostmz/" rel="bookmark">painful reactions. Transport or industrial noise has a depressing effect on a person - it tires, irritates, interferes with concentration. As soon as such noise stops, a person experiences a feeling of relief and peace .
Noise levels of 20–30 decibels (dB) are practically harmless to humans. This is a natural noise background, without which human life is impossible. For “loud sounds”, the maximum allowable limit is approximately 80–90 decibels. A sound of 120–130 decibels already causes pain in a person, and at 150 it becomes unbearable for him. The effect of noise on the body depends on age, auditory sensitivity, duration of action.
The most detrimental to hearing are long periods of continuous exposure to high-intensity noise. After exposure to strong noise, the normal threshold of auditory perception rises markedly, that is, the lowest level (loudness) at which a given person can still hear a sound of a particular frequency. Hearing threshold measurements are made in specially equipped rooms with a very low level of ambient noise, giving sound signals through headphones. This technique is called audiometry; it allows you to get a curve of individual hearing sensitivity, or an audiogram. Usually, deviations from normal hearing sensitivity are noted on audiograms (see figure).
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Noise source
Noise level (dB)
BUT. working vacuum cleaner
B. noise in the subway
AT. pop music orchestra
G. automobile
D. whisper at a distance of 1 m
8) C, B, D and A
Correct answer: 1
There are many interesting things in the world. The twinkling of stars is one of the most amazing phenomena. How many different beliefs are connected with this phenomenon! The unknown always scares and attracts at the same time. What is the nature of such a phenomenon?
Influence of the atmosphere
Astronomers have made an interesting discovery: the twinkling of stars has nothing to do with their changes. Then why do the stars twinkle in the night sky? It's all about the atmospheric movement of cold and hot air flows. Where warm layers pass over cold ones, air vortices form there. Under the influence of these vortices, the light rays are distorted. So the light rays are bent, changing the apparent position of the stars.
An interesting fact is that the stars do not twinkle at all. Such a vision is created on earth. The eyes of observers perceive the light coming from the star as it passes through the atmosphere. Therefore, the question of why the stars twinkle can be answered that the stars do not twinkle, and the phenomenon that we observe on earth is a distortion of the light that has traveled from the star through the atmospheric layers of air. If such air movements did not occur, then the twinkling would not be observed, even from the most distant star in space.
scientific explanation
If we reveal in more detail the question of why stars twinkle, then it is worth noting that this process is observed when light from a star passes from a denser atmospheric layer to a less dense one. In addition, as mentioned above, these layers are constantly moving relative to each other. We know from the laws of physics that warm air rises and cold air sinks. It is when light passes this layer boundary that we observe flicker.
Passing through the layers of air, different in density, the light of the stars begins to flicker, and their outlines blur and the image increases. In this case, the intensity of the radiation and, accordingly, the brightness also change. Thus, by studying and observing the processes described above, scientists have understood why stars twinkle, and their twinkling varies in intensity. In science, this change in light intensity is called scintillation.
Planets vs Stars: What's the Difference?
An interesting fact is that not every cosmic luminous object emits light from the scintillation phenomenon. Let's take planets. They also reflect sunlight, but do not flicker. It is by the nature of the radiation that a planet is distinguished from a star. Yes, the light of a star gives a twinkling, but the planets do not.
Since ancient times, mankind has learned to navigate in space by the stars. In those days when precise instruments were not invented, the sky helped to find the right path. And today this knowledge has not lost its significance. Astronomy as a science was born in the 16th century when the telescope was first invented. It was then that they began to closely observe the light of stars and study the laws by which they twinkle. Word astronomy in Greek it means "the law of the stars".
Star science
Astronomy studies the Universe and celestial bodies, their movement, location, structure and origin. Thanks to the development of science, astronomers have explained how a twinkling star in the sky differs from a planet, how the development of celestial bodies, their systems, and satellites takes place. This science has looked far beyond the boundaries of the solar system. Pulsars, quasars, nebulae, asteroids, galaxies, black holes, interstellar and interplanetary matter, comets, meteorites and everything related to outer space are studied by the science of astronomy.
The intensity and color of the twinkling starlight is also affected by the height of the atmosphere and the proximity to the horizon. It is easy to see that the stars located close to it shine brighter and shimmer in different colors. This spectacle becomes especially beautiful on frosty nights or immediately after rain. At these moments, the sky is cloudless, which contributes to a brighter shimmer. Sirius has a special radiance.
Atmosphere and starlight
If you want to observe the stellar twinkling, you should understand that with a calm atmosphere at the zenith, this is only occasionally possible. The brightness of the light flux is constantly changing. This is again due to the deflection of light rays, which are unevenly concentrated over the earth's surface. The wind also influences the starry landscape. In this case, the observer of the stellar panorama constantly finds himself alternately in a darkened or illuminated area.
When observing stars located at an altitude of more than 50 °, the change in color will not be noticeable. But the stars that are below 35 ° will twinkle and change color quite often. Very intense flickering indicates the heterogeneity of the atmosphere, which is directly related to meteorology. During the observation of stellar twinkling, it was noticed that it tends to intensify at reduced atmospheric pressure and temperature. An increase in flicker can also be seen with increasing humidity. However, it is impossible to predict the weather from scintillation. The state of the atmosphere depends on a large number of different factors, which does not allow one to draw conclusions about the weather only from stellar twinkling. Of course, some points work, but so far this phenomenon has its own ambiguities and mysteries.
Quest Source: Decision 4555. OGE 2017 Physics, E.E. Kamzeev. 30 options.
Task 20. Refraction in the text refers to the phenomenon
1) changes in the direction of propagation of the light beam due to reflection at the boundary of the atmosphere
2) changes in the direction of propagation of the light beam due to refraction in the Earth's atmosphere
3) absorption of light as it propagates in the Earth's atmosphere
4) rounding of obstacles by a light beam and thereby deviations from rectilinear propagation
Solution.
Before a beam of light from a distant space object (such as a star) can enter the observer's eye, it must pass through the earth's atmosphere. In this case, the light beam undergoes the processes of refraction, absorption and scattering.
Refraction of light in the atmosphere is an optical phenomenon caused by the refraction of light rays in the atmosphere and manifests itself in the apparent displacement of distant objects (for example, stars observed in the sky). As a light beam from a celestial body approaches the Earth's surface, the density of the atmosphere increases (Fig. 1), and the rays are refracted more and more. The process of propagation of a light beam through the earth's atmosphere can be modeled using a stack of transparent plates, the optical density of which changes as the beam propagates.
Due to refraction, the observer sees objects not in the direction of their actual position, but along a tangent to the ray path at the point of observation (Fig. 3). The angle between the true and apparent directions of an object is called the angle of refraction. Stars near the horizon, whose light must pass through the largest thickness of the atmosphere, are most subject to the action of atmospheric refraction (the refraction angle is about 1/6 of an angular degree).
The Greek astronomer Claudius Ptolemy (circa 130 AD) is the author of a remarkable book that served as the main textbook on astronomy for nearly 15 centuries. However, in addition to the astronomical textbook, Ptolemy also wrote the book Optics, in which he outlined the theory of vision, the theory of flat and spherical mirrors, and the study of the phenomenon of light refraction. Ptolemy encountered the phenomenon of light refraction while observing the stars. He noticed that a beam of light, passing from one medium to another, "breaks". Therefore, a stellar ray, passing through the earth's atmosphere, reaches the surface of the earth not in a straight line, but along a curved line, that is, refraction occurs. The curvature of the beam path occurs due to the fact that the air density changes with height.
To study the law of refraction, Ptolemy conducted the following experiment. He took the circle and fixed the rulers l1 and l2 on the axis so that they could freely rotate around it (see figure). Ptolemy immersed this circle in water up to the diameter AB and, turning the lower ruler, ensured that the rulers lay for the eye on one straight line (if you look along the upper ruler). After that, he took the circle out of the water and compared the angles of incidence α and refraction β. He measured angles with an accuracy of 0.5°. The numbers obtained by Ptolemy are presented in the table.
Ptolemy did not find a "formula" of the relationship for these two series of numbers. However, if you determine the sines of these angles, it turns out that the ratio of the sines is expressed by almost the same number, even with such a rough measurement of the angles that Ptolemy resorted to.
Due to the refraction of light in a calm atmosphere, the apparent position of the stars in the sky relative to the horizon
1) above actual position
2) below actual position
3) shifted in one direction or another vertically relative to the actual position
4) matches the actual position
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In a calm atmosphere, the positions of stars that are not perpendicular to the surface of the Earth at the point where the observer is located are observed. What is the apparent position of the stars - above or below their actual position relative to the horizon? Explain the answer.
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Refraction in the text refers to the phenomenon
1) changes in the direction of propagation of a light beam due to reflection at the boundary of the atmosphere
2) changes in the direction of propagation of a light beam due to refraction in the Earth's atmosphere
3) absorption of light as it propagates through the earth's atmosphere
4) light beam bending around obstacles and thus deflecting rectilinear propagation
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Which of the following conclusions contradicts Ptolemy's experiments?
1) the angle of refraction is less than the angle of incidence when the beam passes from air to water
2) as the angle of incidence increases, the angle of refraction increases linearly
3) the ratio of the sine of the angle of incidence to the sine of the angle of refraction does not change
4) the sine of the angle of refraction depends linearly on the sine of the angle of incidence
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Photoluminescence
Some substances, when illuminated by electromagnetic radiation, begin to glow themselves. This glow, or luminescence, has an important feature: the luminescence light has a different spectral composition than the light that caused the glow. Observations show that luminescence light has a longer wavelength than the exciting light. For example, if a beam of violet light is directed to a cone with a solution of fluorescein, then the illuminated liquid begins to luminesce brightly with green-yellow light.
Some bodies retain the ability to glow for some time after their illumination has ceased. Such an afterglow can have a different duration: from fractions of a second to many hours. It is customary to call a glow that stops with lighting, fluorescence, and a glow that has a noticeable duration, phosphorescence.
Phosphorescent crystalline powders are used to coat special screens that remain luminous for two to three minutes after illumination. Such screens also glow under the action of X-rays.
Phosphorescent powders have found a very important application in the manufacture of fluorescent lamps. In gas-discharge lamps filled with mercury vapor, when an electric current passes, ultraviolet radiation is produced. Soviet physicist S.I. Vavilov proposed to cover the inner surface of such lamps with a specially made phosphorescent composition, which, when irradiated with ultraviolet, gives visible light. By selecting the composition of the phosphorescent substance, it is possible to obtain the spectral composition of the emitted light, as close as possible to the spectral composition of daylight.
The phenomenon of luminescence is characterized by extremely high sensitivity: sometimes 10 - - 10 g of a luminous substance, for example, in solution, is enough to detect this substance by its characteristic glow. This property is the basis of luminescent analysis, which makes it possible to detect negligible impurities and to judge about impurities or processes that lead to a change in the original substance.
Human tissues contain a wide variety of natural fluorophores, which have different fluorescence spectral regions. The figure shows the emission spectra of the main fluorophores of biological tissues and the scale of electromagnetic waves.
According to the given data, pyroxidine glows
1) red light
2) yellow light
3) green light
4) purple light
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Two identical crystals, having the property of phosphorescence in the yellow part of the spectrum, were preliminarily illuminated: the first with red rays, the second with blue rays. For which of the crystals will it be possible to observe an afterglow? Explain the answer.
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When examining food products, the luminescent method can be used to detect spoilage and falsification of products.
The table shows the indicators of the luminescence of fats.
Butter luminescence color changed from yellow-green to blue. This means that the butter could have added
1) only butter margarine
2) only margarine "Extra"
3) only vegetable fat
4) any of the specified fats
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Earth Albedo
The temperature at the Earth's surface depends on the reflectivity of the planet - albedo. Surface albedo is the ratio of the energy flux of reflected sunlight to the energy flux of solar rays incident on the surface, expressed as a percentage or fraction of a unit. The Earth's albedo in the visible part of the spectrum is about 40%. In the absence of clouds, it would be about 15%.
Albedo depends on many factors: the presence and condition of cloudiness, changes in glaciers, seasons, and, accordingly, on precipitation.
In the 90s of the XX century, the significant role of aerosols - "clouds" of the smallest solid and liquid particles in the atmosphere became obvious. When fuel is burned, gaseous oxides of sulfur and nitrogen enter the air; combining in the atmosphere with water droplets, they form sulfuric, nitric acids and ammonia, which then turn into sulfate and nitrate aerosols. Aerosols not only reflect sunlight without letting it through to the Earth's surface. Aerosol particles serve as nuclei for the condensation of atmospheric moisture during the formation of clouds and thereby contribute to an increase in cloudiness. And this, in turn, reduces the influx of solar heat to the earth's surface.
Transparency for solar rays in the lower layers of the earth's atmosphere also depends on fires. Due to fires, dust and soot rise into the atmosphere, which cover the Earth with a dense screen and increase the surface albedo.
Which statements are true?
BUT. Aerosols reflect sunlight and thus contribute to a decrease in the Earth's albedo.
B. Volcanic eruptions contribute to an increase in the Earth's albedo.
1) only A
2) only B
3) both A and B
4) neither A nor B
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The table shows some characteristics for the planets of the solar system - Venus and Mars. It is known that the albedo of Venus A 1= 0.76, and the albedo of Mars A 2= 0.15. Which of the characteristics mainly influenced the difference in the albedo of the planets?
1) BUT 2) B 3) AT 4) G
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Does the Earth's albedo increase or decrease during volcanic eruptions? Explain the answer.
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Surface albedo is understood as
1) the total amount of sunlight falling on the earth's surface
2) the ratio of the energy flux of reflected radiation to the flux of absorbed radiation
3) the ratio of the energy flux of reflected radiation to the flux of incident radiation
4) the difference between the incident and reflected radiation energy
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Spectra study
All heated bodies radiate electromagnetic waves. To experimentally study the dependence of the radiation intensity on the wavelength, it is necessary:
1) expand the radiation into a spectrum;
2) measure the energy distribution in the spectrum.
To obtain and study spectra, spectral devices - spectrographs - are used. The scheme of the prism spectrograph is shown in the figure. The studied radiation first enters the tube, at one end of which there is a screen with a narrow slit, and at the other - a converging lens L one . The slit is at the focus of the lens. Therefore, a divergent light beam that enters the lens from the slit exits it in a parallel beam and falls on the prism R.
Since different frequencies correspond to different refractive indices, then parallel beams of different colors come out of the prism, which do not coincide in direction. They fall on the lens L 2. At the focal length of this lens is a screen, frosted glass or photographic plate. Lens L 2 focuses parallel beams of rays on the screen, and instead of a single slit image, a whole series of images is obtained. Each frequency (more precisely, a narrow spectral interval) has its own image in the form of a colored strip. All these images together
and form a spectrum.
The radiation energy causes the body to heat up, so it is enough to measure the body temperature and use it to judge the amount of energy absorbed per unit time. As a sensitive element, one can take a thin metal plate covered with a thin layer of soot, and by heating the plate, one can judge the radiation energy in a given part of the spectrum.
The decomposition of light into a spectrum in the apparatus shown in the figure is based on
1) light dispersion phenomenon
2) phenomenon of light reflection
3) light absorption phenomenon
4) thin lens properties
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In the device of a prism spectrograph, the lens L 2 (see figure) is used for
1) decomposition of light into a spectrum
2) focusing rays of a certain frequency into a narrow strip on the screen
3) determining the intensity of radiation in different parts of the spectrum
4) converting a divergent light beam into parallel beams
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Is it necessary to cover the metal plate of the thermometer used in the spectrograph with a layer of soot? Explain the answer.
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