I. Find out the words in the dictionary. Write them down and learn

X. Practice with someone asking and answering.

1. What does the part of the electromagnetic spectrum with very short wavelengths and very high frequency correspond to?

2. What can X-rays and gamma-rays cause?

3. What have studies of heavenly bodies from artificial satellites revealed?

4. Why do the observations have to be made from space?

5. How are X-rays produced?

6. Why are commercial X-ray machines heavily insulated and shielded with lead?

7. In what spheres are the best-known uses of X-rays?

8. When are gamma-rays emitted?

9. What is the main difference between two types of radiation?

10. What do the properties of gamma-rays resemble?

11. Are gamma-rays important in the study of the ultimate structure of matter?

XI. Put questions to the following sentences.

1. X-rays are one of the types of radiation emitted by some stars and galaxies. (General)

2. Studies of heavenly bodies from artificial satellites have revealed various X-ray sources, among which are possible locations of black holes. (General)

3. Here on earth, X-rays are generated artificially. (Disjunctive)

4. The X-ray beam is emitted at right angles to the electron beam. (Alternative)

5. X rays are produced by bombardment of atoms with high-energy electrons. (Special)

6. Gamma-rays derive from the excitation of the atomic nucleus itself. (General)

7. Characteristic radiation is emitted when the excited electrons or nucleons return to their original energy levels. (Special)

8. Gamma rays often occur as product of collisions between high energy subatomic particles. (Disjunctive)

XII. Dictate the following sentences in English to your fellow-students. Check them together.

1. X-rays are one of the types of radiation emitted by some stars and galaxies.

2. X-rays are produced using thermionic vacuum tubes that operate at potentials of up to 2 million volts.

3. The X-ray beam is emitted at right angles to the electron beam.

4. The main difference between the two types of radiation is in their origins.

5. The properties of gamma-rays resemble those of X-rays.

6. In research into particle physics, gamma-rays often occur as product of collisions between high-energy subatomic particles.

UNIT 18

I. Find out the words in the dictionary. Write them down and learn.

alternate, to alter, compression, rarefaction, originate, vocal

cords, throat, drum, string, to convert, longitudinal, transverse, prop-

agation, large-coiled, backward and forward, to bunch, to occur, to

distinguish, pure, pitch, intensity, to assess, to perceive, to diminish,

to affect

II. Read the text. Use a dictionary, if necessary.

TEXT: «SOUND»

Sound consists of waves of alternate compression and rarefaction that transmit kinetic energy through a medium. If there is no medium, there is no sound; sound waves cannot pass through a vacuum. All sounds originate from vibrating objects, such as the vocal cords in the human throat, the skin of a drum, or the strings of a violin. The vibrations are then passed on through a medium – most commonly air – until they strike the ear drum; the ear converts the vibrations into nerve impulses, which pass to the brain where they are interpreted as sounds. Microphones are the other most common instruments of sound waves into electrical signals. Waves and sound. There are two types of waves in physics: longitudinal and transverse. Sound waves are of the longitudinal type – that is, their vibrations take place in the same direction as they travel. The phenomenon of longitudinal wave propagation can be demonstrated with a long, large-coiled spring. When the string is fixed at one end and the other end is moved backwards and forwards, alternating regions of compression (where the coils are bunched together) and rarefaction (where the coils are farther apart than normal) move along the spring. Transverse waves are those in which the vibrations occur at right angles to the direction, in which the waves travel – as happens, for example, when a length of rope is moved regularly up and down to give it a wavelike appearance. Ocean waves and light waves also travel by transverse propagation. Frequency and intensity. Two obvious ways of distinguishing one «pure» sound (that is, a «pure» tone) from another are by their pitch and loudness. Neither property is a scientifically accurate notion. Pitch is a word used by musicians and is closely related to frequency; but it is a subjective term, whereas frequency can be measured physically. Similarly loudness, closely related to a sound’s intensity, differs according to the sensitivity of the hearer’s ears, whereas intensity can be measured in exact physical quantities. (Real sounds are mixtures of many different pure sounds and also have a characteristic «quality», which can be assessed by detailed examination of the shape of a real sound’s waveform.) The frequency of a sound wave is the number of wavelengths that are completed in a given period of time. The universal unit of measurement is the hertz (Hz), which represents one complete wavelength, or cycle, per second. The human ear is sensitive to sound in the frequency range from about 20 Hz. As people grow older, their ability to perceive high frequencies diminishes. The intensity of sound is measured in terms of the amount of power that passes each second through a given area perpendicular to the direction of the sound wave. The intensity unit is the decibel (db). There is no absolute decibel scale; it is a relative scale. Velocity. Sound can be transmitted by any medium – gas, liquid, or solid – and all sound waves travel at a constant velocity through any given medium at a constant temperature. But depending on their elastic ity and density, some mediums transmit waves faster than others. It is extremely difficult for sound waves to pass from a medium of one density to another of a much higher or lower density. Anything that changes the density of a medium also alters the speed at which sound travels through it. Hence the velocity of sound is affected by temperature; as the temperature increases, the medium expands. Its density decreases, with the result that the velocity of sound increases.

III. Find the sentences that can’t be found in the text.

1. A sound wave consists of a series of alternate compressions and rarefactions of the medium through which it passes.

2. Waves of alternate compression and rarefaction transmit kinetic energy through a medium.

3. The vibrations pass through a medium and it works by converting sound waves into electrical signals.

4. The power of sound, perceived as loudness, is measured in decibels.

5. The decibels scale is a relative one, with an arbitrary zero point (usually taken as the lower threshold of human hearing).

6. There are two types of waves in physics: longitudinal and transverse.

7. As with longitudinal waves along a spring, sound waves consist of a series of compressions and rare factions.

8. The wavelength is the distance between two adjacent points (or particles) that are in the identical phase of the wave’s vibration.

IV. Translate the following noun groups into Uzbek.

1. the skin of drum _______________________________________

2. the strings of violin ____________________________________

3. common instruments of sound detection ____________________

4. phenomenon of longitudinal wave propagation ______________

5. regions of compression _________________________________

6. sensitivity of the hearer’s ears ___________________________

7. mixtures of pure sounds ________________________________

8. detailed examination of the shape ________________________

9. the shape of a real sound’s waveform ______________________

10. frequency of a sound wave _____________________________

11. number of wavelengths ________________________________

12. intensity of sound ____________________________________

13. a medium of one density _______________________________

14. velocity of sound _____________________________________

VI. Find Uzbek equivalents to the following words and expressions in the text.

1. alternate compression _________________________________

2. originate from vibrating objects _________________________

3. sound detection _____________________________________

4. to be father apart _____________________________________

5. to move backward and forward __________________________

6. right angle __________________________________________

7. to move up and down __________________________________

8. a scientifically accurate notation _________________________

9. to be completed in a given period of time __________________

10. intensity unit _______________________________________

11. as the temperature increases ___________________________

12. the medium expands __________________________________

VII. Fill in the missing words.

1. Sound consists of waves of _____ compression and _____.

2. If there is no _____, there is no sound.

3. Sound waves are of the _____ type – that is their vibrations take place in the same direction as they _____.

4. When the spring is fixed at one end and the other end is moved _____ and _____.

5. _____ waves are those in which the vibrations occur at _____ _____ to the direction

6. Ocean waves and light waves also travel by transverse _____.

7. The obvious ways of distinguishing sound are by their _____ and _____.

8. Real sounds are _____ of many different pure sounds.

9. The universal unit is the _____.

10. The velocity of sound is _____ by temperature.

VIII. Fill in the preposition, if necessary.

1. Sound waves cannot pass ___ a vacuum.

2. All sounds originate ___ vibrating objects.

3. The vibrating objects are then passed ___ ___ a medium.

4. The phenomenon of longitudinal wave propagation can be demonstrated ___ a long, large-coiled spring.

5. Pitch is a word used ___ musicians, and it is closely related ___ frequency.

6. Frequency can be measured ___ physically.

7. The human ear is sensitive ___ sound ___ the frequency range ___ ___ Hz.

8. The intensity of sound is measured ___ terms of the amount of power.

IX. Define whether sentences are true or false.

1. All sounds originate from still and vibrating objects, because all objects have their own waves.

2. Microphones can’t be instruments of sound direction, because we used them just to close our ears.

3. When the spring is fixed at one end and the other end is moved backward and forward, alternating regions of compression move along the spring.

4. Loudness, closely related to a sound’s density, and depends on the sensivity of the hearer’s ears.

5. The frequency of a sound wave is the number of vibrations that are completed in a given period of time.

6. The human ear is sensitive to sound in the frequency range from about 10 Hz.

7. As people grow older, they loose their ability to perceive high frequencies.

8. The intensity of sound is the amount of power that passes each second through a given area perpendicular to the direction of the sound wave.

9. There is absolute decibel scale.

10. Sound waves depend on velocity and temperature of a medium.

X. Practice with someone asking and answering.

1. What originates from vibrating objects?

2. How can all living beings hear sounds?

3. What are the types of waves in physics?

4. What kind of experiment can show us the phenomenon of longitudinal wave propagation?

5. Are there any ways of distinguishing one «pure» sound from another object? What are these ways, if any?

6. What is intensity of sound?

7. How does sound depend on medium and temperature?

XI. Put questions to the following sentences.

1. Sound waves cannot pass through a vacuum. (Disjunctive)

2. The ear converts the vibrations into nerve impulses. (Special)

3. Microphones are the most common instruments of sound detection. (What)

4. Frequency can be measured physically (General)

5. Decibel scale is a relative scale. (Alternative)

XII. Dictate the following text in English to your fellow-students.

1. A sound wave consists of a series of alternate compressions and rarefactions of medium.

2. Alternate compression and rarefaction transmit kinetic energy through a medium which they pass.

3. Sound can not pass through a vacuum.

4. Vocal cords in human throat, the skin of a drum or the strings of a violin are good examples of vibrating objects.

5. The phenomenon of longitudinal wave propagation can be demonstrated with a long large spring.

6. Each complete wave cycle is made up of one compression and one rarefaction.

7. The wavelength is the distance between two adjacent point, that are in the identical phase of the wave’s vibration.

UNIT 19

I. Find out the words in the dictionary. Write them down and learn.

to remove, cluster, excess, to cancel, to rub, to constitute, suffi-

ciently, to conduct, to contribute, insulator, to repel, to redistribute,

to acquire, to undergo

II. Read the text. Use a dictionary, if necessary.

TEXT: «ELECTRICITY»

Electricity and all its observable effects result from properties of stationary or moving electric charges. There are two types, known as positive charges and negative charges, which exist in all substances and in all states of matter – solid, liquid, and gas. All substances are made up of atoms, which consist of a nucleus (containing protons and neutrons) and orbiting electrons. Protons are positively charged, and electrons are negatively charged. Electrons can be removed from atoms and made to take part in various electrical phenomena. Protons, on the other hand, are usually found as part of a cluster of protons, neutrons, and electrons known as an ion. Ions may be positively or negatively charged, depending on whether they have an excess of protons or electrons. In an ordinary piece of material the numbers of protons and electrons within each atom, and therefore within the material as a whole, are equal. The positive and negative charges cancel each other to a large extent, and no electrical effects are observed. But if extra charges of one type are added, the material is left with a net charge and electrical effects result. Charges can be transferred from one material to another by rubbing them together. The study of these net stationary charges and their effects on each other constitutes the subject of static electricity or electrostatics. In certain solid materials – metals in particular – some electrons are sufficiently «free» to be able to move through the material in a stream, forming an electric current. This is the basis of current electricity. Solids, liquids, and gases can all conduct electric current if there are enough free electrons or ions. Electrons and positively charged ions move in opposite directions through the material, but in general both contribute to the current in a conducting medium. In an insulator, the electrons are too firmly fixed by chemical bonding to be able to move, and the material does not normally conduct electricity. Static electricity. Static electricity can be produced by rubbing an insulating material such as a polyethylene rod with dry cloth. Charges are transferred so that the polyethylene is left with a net charge of one type and the cloth with a net charge of the other type. The rod and cloth then attract each other. On the other hand, two rubbed rods of the same material repel, and the two cloths repel. Unlike charges thus experience a force of attraction, whereas like charges repel each other. It is impossible to find a material that is repelled by both polyethylene and cloth. Electrostatic induction. Although nothing is repelled by both polyethylene and cloth, uncharged pieces of material (for example, small scraps of paper) are attracted to both. This results from a phenomenon called electrostatic induction. The paper is neutral overall, but the influence of the charged polyethylene redistributes the charges in the paper. The polyethylene is positively charged and exerts an attractive force on the paper's negative charges The net result is mutual attraction. Coulomb's law and electric field. The forces of electrostatic attraction and repulsion between charged objects are caused by the electric fields associated with them. The magnitude of the force between two charges depends on their size, distance apart, and the substance they are in. The force is proportional to the product of the charges, and inversely proportional to the square of the distance between them – a relationship known as Coulomb's law. The force also decreases if the charges are placed in a material that undergoes electrical polarization, which separates the charges and has the effect of partly shielding them from each other. The amount of shielding is quantified by a property called the permittivity of a substance. A vacuum, which cannot undergo polarization, has the lowest permittivity, called the permittivity of free space. The permittivity of other materials depends on their structure; ionic substances such as water, for example, generally have higher permittivities than non-ionic substances. III. Find the sentences that can’t be found in the text.

1. Modern physics defines the electromagnetic field as a distinct form of matter possessing definite properties.

2. The positive and negative charges cancel each other to a large extent, and no electrical effects are observed.

3. Electrons and positively charged ions move in opposite directions through the material, but in general both contribute to the current in a conducting medium.

4. The magnitude of the force between two charges depends on their size, distance apart, and the substance they are in.

5. In the case of a stationary charged body the magnetic fields, built up by the elementary charges constantly moving inside it cancel each other, and there is practically no magnetic field.

V. Find Uzbek equivalents to the following expressions in the text.

1. permittivity _________________________________________

2. as a whole __________________________________________

3. to a large extent ______________________________________

4. in particular _________________________________________

5. in general ___________________________________________

6. whereas ____________________________________________

7. to exert an attractive force _____________________________

8. inversely proportional _________________________________

9. thus _______________________________________________

10. polyethylene rod _____________________________________

VI. Fill in the missing words.

1. There are two types, known as positive charges and negative

charges, which exist in all _______ and in all _______ of matter _______ solid, liquid and gas.

2. Electrons can be removed from atoms and made to _______ _______ in various electrical phenomena.

3. The positive and negative charges _______ each other to a large extent, and no electrical effects are.

4. Solids, liquids and gases can all _______ electric current if there are enough _______ electrons or ions.

5. The polyethylene is positively charged and _______ an _______ force on the paper’s negative charges.

6. The forces of electrostatic _______ and _______ between objects are caused by the _______ fields associated with them.

7. The force is proportional to the _______ of the charges, and _______ proportional to the square of the distance between them.

VII. Fill in the prepositions, if necessary.

1. Electrons can be removed ___ atoms and made to take part ___ various electrical phenomena.

2. Protons, ___ the other hand, are usually found as part ___ a cluster ___ protons, neutrons, and electrons known as an ion.

3. Charges can be transferred ___ one material ___ another ___ rubbing them together.

4. The study ___ these net stationary charges and their effects ___ each other constitutes ___ the subject ___ static electricity or electro statics.

5. It is impossible to find a material that is repelled ___ both polyethylene and cloth.

6. This results ___ a phenomenon called electrostatic induction.

7. The magnitude ___ the force between two charges depends ___

their size, distance apart, and the substance they are ___.

VIII. Define whether the sentences are true or false.

1. Electricity and all its observable effects result from properties of stationary electric charges.

2. Electrons can’t be removed from atoms.

3. Protons are usually found as part of a cluster of protons, neutrons, and electrons known as an ion.

4. Liquids and gases can’t conduct electric current even if there are enough free electrons.

5. Static electricity can be produced by rubbing an insulating material such as a polyethylene rod with a dry cloth.

6. It is easy to find a material that is repelled by both polyethylene and cloth.

7. A vacuum, which cannot undergo polarization, has the lowest permittivity, called the permittivity of free space.

IX. Practice with someone asking and answering.

1. What do electricity and all its observable effects result from?

2. How can charges be transferred from one material to another?

3. Can solids, liquids and gases conduct electric current?

4. How can static electricity be produced?

5. Is it possible to find a material that is repelled by both polyethylene and cloth?

6. What are the forces of electrostatic attraction and repulsion between charged objects caused by?

7. What does the magnitude of the force between two charges depend on?

8. What relationship is known as Coulomb’s law?

9. What is the permittivity of a substance?

X. Put questions to the following sentences.

1. There are two types, known as positive charges and negative

charges. (Disjunctive)

2. Electrons can be removed from atoms and made to take part in various electrical phenomena. (General)

3. The positive and negative charges cancel each other to a large extent. (General)

4. This results from a phenomenon called electrostatic induction. (Special)

5. Unlike charges experience a force of attraction. (Alternative)

6. The forces of electrostatic attraction and repulsion between charged objects are caused by the electric fields associated with them. (What...?)

XI. Dictate the following sentences in English to your fellow-students. Check them together.

1. All substances are made up of atoms, which consist of a nucleus and orbiting electrons.

2. Electrons can be removed from atoms and made to take part in various electrical phenomena.

3. Charges can be transferred from one material to another by rubbing them together.

4. The forces of electrostatic attraction and repulsion between charged objects are caused by the electric fields associated with them.

UNIT 20

I. Find out the words in the dictionary. Write them down and learn.

processing, to convey, device, to manipulate, to reduce, to am-

plify, to vary, to be subjected, intermediate, lattice, to free, boron,

excess, junction