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

III. Find an adjective in each line and translate it. Translate also

the underlined words.

a) Invisible, frequency, comprise, generally, density;

b) Detect, transparent, uncertainty, source, naturally;

c) Wavelength, field, vast, inversely, ray;

d) Application, uncommonly, emit, particularly, magnetic;

e) Impossible, microwave, quanta, consist of, molecule;

f) Absorb, current, various, traverse, spectra;

g) Penetrate, emptiness, slightly, cell, dual;

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

1. Energy may take various forms – sound, chemical and electrical energy, for example.

2. The various forms of radiant energy have many common characteristics, the most fundamental of which concerns their nature.

3. Another basic characteristic of electromagnetic radiation is the fact that it does not need a medium in which to travel.

4. The speed of light in air is nearly the same as its speed in a vacuum and for practical purposes they are regarded as being identical.

5. In a vacuum all forms of electromagnetic radiation travel at the same constant velocity.

6. A beam of white light is dispersed into spectral colours when it passes into a prism or lens.

V. Put the following sentences in the right order.

1. The various types of radiant energy have different wavelengths and frequencies.

2. Radiant energy can be detected only when it is absorbed and brings about an observable effect.

3. Another basic characteristic of electromagnetic radiation is the fact that it does not need a medium in which to travel.

4. In a vacuum all forms of electromagnetic radiation travel at the same constant velocity.

5. One whole range of related forms of energy is known as radiant energy.

6. Radiant energy has a dual wave/particle nature.

VI. Give Uzbek equivalents to the following words and expressions and find them in the text.

1. to make up the electromagnetic spectrum ___________________

2. to comprise X-rays and gamma-rays _______________________

3. can be detected ______________________________________

4. practical applications __________________________________

5. to be emitted by the sun _________________________________

6. life would be impossible ________________________________

7. can be considered as being made up of «particles» ____________

8. to penetrate body tissues ________________________________

9. to pass through metal __________________________________

10. called the speed of light _______________________________

11. to be nearly the same as ________________________________

12. equal to more than ___________________________________

13. in the case of visible light ______________________________

14. to be inversely proportional to ___________________________

15. to bring about an observable effect _______________________

VII. Translate the following noun groups into Uzbek.

1. range of related forms _________________________________

2. particular rangers of wavelengths and frequencies ____________

3. special types of photographic film ________________________

4. infrared and microwave heating __________________________

5. common characteristics _______________________________

6. vast emptiness of space ________________________________

7. the speed of light _____________________________________

8. density of the medium __________________________________

9. retina of the eye _______________________________________

IX. Fill in the missing words.

1. One whole _______ of related forms is known as radiant _______ or electromagnetic radiation.

2. Almost all have found practical _______ in radio communication, radar and so on.

3. The most important forms of electromagnetic radiation are _______ light.

4. The most fundamental radiant energy characteristics _______ their nature.

5. Another basic characteristic of electromagnetic radiation is the fact that it does not need a _______ in which to travel.

6. All forms of electromagnetic radiation travel at the same constant _______.

7. Radiant energy can be _______ only when it is absorbed.

8. Gamma rays ionize certain gases when _______ by their molecules.

X. Fill in the preposition if necessary.

1. Radiant energy and range of related forms make ____ in electromagnetic spectrum.

2. Low-frequency end of the spectrum are radio waves, followed ____ microwaves.

3. Apart ____ light, all are invisible to the human eye.

4. The most fundamental characteristics of radiant energy concern ____ their nature.

5. Electromagnetic radiation does not need ____ a medium ____ which to travel.

6. All forms of electromagnetic radiation travel ____ the same constant velocity.

7. These two characteristics multiplied ____ the frequency are equal ____ the velocity.

8. X-rays and visible light cause ____ chemical changes ____ a photographic emulsion.

XI. Define whether sentences are true or false.

1. Energy may take only two forms – sound and electrical energy.

2. Visible light and ultraviolet radiation come before microwaves and infrared radiation.

3. Only X-rays and gamma-rays have found practical application.

4. Various forms of radiant energy can be considered as being mad up of «particles», or quanta.

5. Light travels through air, water and glass and X-rays, gamma rays can penetrate body tissues and even pass through metal.

6. In a vacuum all forms of electromagnetic radiation don’t travel at all.

7. The speed of light varies greatly in the air and in a vacuum.

8. The various types of radiant energy don’t have different wavelengths and frequencies.

XII. Practice with someone asking and answering.

1. What is known as radiant energy?

2. What makes up the electromagnetic spectrum?

3. What can be detected by electronic devices and special types of photographic film?

4. Why do the various forms of radiant energy have many common characteristics?

5. What is called the speed of light?

6. What can you say about the speed of light in the air and in a vacuum?

7. When can radiant energy be detected?

XIII. Put questions to the following sentences.

1. Various radiations are characterized by particular ranges of wavelengths and frequencies (General).

2. The shortest wavelengths and highest frequencies comprise X-rays and gamma-rays (What?)

3. Metal is «transparent» to X-rays and gamma-rays (General)

4. The velocity is constant in any particular medium (Alternative).

5. Gamma-rays ionize certain gases (Disjunctive).

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

1. Energy takes various forms – sound and electrical energy, for example.

2. The range of related forms is known as radiant energy or electromagnetic radiation.

3. Electromagnetic radiation can traverse the vast emptiness of space.

4. Only visible light, radio waves and some infrared and ultraviolet radiation can penetrate the earth’s atmosphere.

5. But the various forms of radiation can travel through other mediums: light travel through air, water, glass, and X-rays, gamma-rays can penetrate body tissues and even pass through metal.

UNIT 11

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

to oscillate, an aerial, frequency, to associate with, a grating,

apparent, wave-particle duality, to resolve, an expanding sphere, to

diminish, phase, coherent, incoherent, to exhibit, to transmit

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

TEXT: «ELECTROMAGNETIC RADIATION»

Electromagnetic radiation results whenever electrons oscillate, decelerate, or change energy levels in an atom. X-rays, for example, are emitted when fast-moving electrons decelerate rapidly, and radio waves (at the opposite end of the electromagnetic spectrum) are produced by oscillating electrons in the metal of transmitting aerials. Waves and particles. Electromagnetic radiation consists of a wave motion in both an electric and magnetic field, which oscillate with the same frequency but at right angles to the direction of travel. Electromagnetic waves are therefore examples of transverse waves. But electromagnetic radiation also has properties associated with particles, and its precise nature is something of an enigma. In some circumstances –such as the diffraction of light by a grating – it acts like a wave, whereas in others – for example, the generation of an electric charge when ultraviolet radiation strikes certain metals (a phenomenon called the photoelectric effect) – it acts like a stream of particles. This apparent waveparticle duality has not been fully resolved. For practical purposes electromagnetic radiation can be considered to behave as a wave motion or as a stream of energy particles. Wave characteristics. Electromagnetic waves are emitted in all directions away from their source. So if the source is a single point, each wave front can be regarded as an expanding sphere. With increasing distance from the source, the intensity of radiation diminishes as the surface area of the sphere increases. The intensity of radiation is thus inversely proportional to the square of the distance travelled. Another important wave characteristic of electromagnetic radia tion is phase. In most sources of radiant energy the atoms emit waves at random intervals. As a result, the vibrations of waves of the same frequency are out of phase with each other – that is, the maximum and minimum strengths of the electric and magnetic fields of one wave do not coincide with those of other waves. Furthermore, although in each single wave the electric and magnetic fields are at right angles to each other, in a collection of waves not all the electric fields (or magnetic ones) lie in the same plane, unless the waves are polarized. Randomlyemitted electromagnetic radiation is described as incoherent, and this is the usual way in which radiant energy is emitted. In lasers, on the other hand, the atoms do not emit randomly and the light produced is coherent – that is, all the waves are in phase. Particle nature. The particle nature of electromagnetic radiation is explained by the quantum theory, according to which radiant energy is emitted in discrete, individual «packets» of energy called quanta or photons. But even the quantum theory cannot explain all the properties of electromagnetic radiation. As a result, wave-particle duality remains fundamental to understanding the nature of radiant energy. Basic Properties. All forms of electromagnetic radiation exhibit several basic properties. One of the most fundamental is velocity: all electromagnetic radiations travel at the same constant velocity through a vacuum. They may also pass through other mediums, although not all mediums are transparent to all types of electromagnetic radiation. X rays, for instance, can pass through metal but light cannot. In transparent mediums the velocity of the radiation is slower than in a vacuum; the exact speed depends on the frequency of radiation and the medium’s density. If electromagnetic radiation is not transmitted through a medium, it may be reflected or absorbed. The other principal properties of electromagnetic radiation are scattering, diffraction, interference, and polarization.

III. Find an adjective in each line and translate it. Translate alsothe underlined words.

a) Apparent, transmit, duality, diminish, inversely;

b) Absorb, source, usual, randomly, coincide;

c) Strengthen, transparent, density, fundamental, decelerate;

d) Fully, exhibit, radiant, coherent, aerial;

e) Oscillate, property, diffract, incoherent, frequently;

f) Quanta, expand, reflect, uncertainty, rapid;

g) Interfere, single, resolve, associate with, velocity;

IV. Practice the following speech patterns.

Pattern 1. Wave front can be regarded as an expanding sphere.

1. Atoms – tiny models of the solar system.

Pattern 2. The particle nature of electromagnetic radiation is

explained by the quantum theory.

1. The force between two charges – Coulomb’s law.

2. The motion of planets – Newton’s laws.

3. The atom and its motion – the quantum theory.

Pattern 3. All forms of electromagnetic radiation exhibit

several basic properties.

1. Solids

2. Liquids

3. Gases

4. Electrons

5. Neutrons

6. Colloids

7. Crystalloids

8. Liquid crystal

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

1. Electromagnetic radiation results whenever electrons oscillate, decelerate or change energy levels in an atom.

2. Electromagnetic radiation consists of a wave motion in both an electric and magnetic field.

3. The joint interplay of electric and magnetic forces is what is called an electromagnetic field.

4. In some circumstances it acts like a wave, whereas in others for example, the generation of an electric charge when ultraviolet radiation strikes certain metals – it acts like a stream of particles.

5. Wave characteristics tend to predominate at the long-wavelength, low frequency (radio wave) end of the electromagnetic spectrum, whereas particle characteristics are more pronounced at the short-wavelength, high-frequency (X-ray and gamma-ray) end.

6. The particle nature of electromagnetic radiation is explained by the quantum theory.

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

1. electromagnetic radiation results _________________________

2. energy levels ________________________________________

3. X-rays _____________________________________________

4. wave motion ________________________________________

5. at right angles ________________________________________

6. direction of travel _____________________________________

7. precise nature ________________________________________

8. something of an enigma ________________________________

9. radiation strikes certain metals ___________________________

10. an expаnding sphere __________________________________

11. emit waves at random intervals __________________________

12. are out of phase with each other __________________________

13. randomly-emitted electromagnetic radiation _______________

14. incoherent radiation _________________________________

15. exhibit several properties _____________________________

16. exact speed _________________________________________

VIII. Analyze the structure of the following sentences.

1. In some circumstances – such as the diffraction of light by a grating – it acts like a wave, whereas in others – for example, the generation of an electric charge when ultraviolet radiation strikes certain metals – it acts like a stream of particles.

2. Furthermore, although in each single wave the electric and magnetic fields are at right angles to each other, in a collection of waves not all the electric fields (or magnetic ones) lie in the same plane, unless the waves are polarized.

3. In lasers the atoms do not emit randomly and the light produced is coherent.

IX. Fill in the missing words.

1. Electromagnetic radiation results whenever electrons ______, ______, or change energy levels in an atom.

2. Electromagnetic radiation consists of a wave motion in both an electric and magnetic field, which oscillate with the same ______ but at right angles to the ______ of travel.

3. Electromagnetic waves are examples of ______ waves.

4. Electromagnetic radiation also has properties ______ with particles.

5. This apparent ______ has not been fully resolved.

6. If the source is a single point, each wave front can be regarded as an ______ ______.

7. ______ is thus inversely proportional to the square of the distance travelled.

8. In most sources of radiant energy the atoms ______ waves at random intervals.

9. Randomly-emitted electromagnetic radiation is described as ______.

10. Radiant energy is emitted in ______, individual «packets» of energy called ______ or ______.

11. All forms of electromagnetic radiation ______ several basic properties.

12. If electromagnetic radiation is not ______ through a medium, it may be reflected or ______.

X. Fill in the prepositions if necessary.

1. Radio waves are produced ___ oscillating electrons ___ the metal ___ transmitting aerials.

2. Electromagnetic radiation consists ___ a wave motion ___ both an electric and magnetic field, which oscillate ___ the same frequency but ___ right angles ___ the direction ___ travel.

3. Electromagnetic radiation has properties associated ___ particles.

4. Electromagnetic waves are emitted ___ all direction ___ ___

their source.

5. The intensity ___ radiation is inversely proportional ___ the square ___ the distance travelled.

6. The atoms emit waves ___ random intervals.

7. As a result, the vibration ___ waves ___ the same frequency are ___ ___ phase ___ each other.

8. In lasers the atoms do not emit randomly and the light produced is coherent ___ that is, all the waves are ___ phase.

9. ___ to quantum theory radiant energy is emitted ___ discrete, individual «packets» ___ energy called quanta or photons.

10. X-rays can pass ___ metal but light cannot.

XI. Practice with someone asking and answering.

1. When does electromagnetic radiation result?

2. What does electromagnetic radiation consist of?

3. Why is its precise nature something of an enigma?

4. What are two important wave characteristics of electromagnetic radiation?

5. By what theory is the particle nature of electromagnetic radiation explained?

6. Can the quantum theory explain all the properties of electromagnetic radiation?

7. What notion (concept) remains fundamental for understanding the nature of radiant energy?

8. What forms of electromagnetic radiation exhibit several basic properties?

9. What is one of the most fundamental properties? Give the definition of it.

10. What happens to electromagnetic radiation if it is not transmit ted through a medium?

11. What are the other principal properties of electromagnetic radiation?

XII. Translate in Uzbek using a dictionary.

Scattering is the random deflection of radiation caused by molecules or small objects reflecting or diffracting the radiation. Diffraction occurs when electromagnetic waves encounter a narrow opening (comparable in size to the wavelength of the radiation) or an obstacle and are bent around the edges of the opening or obstacle. This phenomenon may be accompanied by interference – the reinforcement or cancellation of waves that occurs when coherent waves of the same frequency interact. And electromagnetic waves can be polarized so that all their electric fields vibrate in the same plane (which necessarily means that their magnetic fields must also oscillate in one plane).

XIII. Dictate the following statements in English to your fellow-students.

1. Electromagnetic radiation consists of a wave motion in both an electric and magnetic field.

2. The apparent wave-particle duality has not been fully resolved.

3. The particle nature of electromagnetic radiation is explained by the quantum theory.

UNIT 12

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

influential, widely accepted, distinguished, a researcher, to

probe, to emerge, bundles of energy, to conclude, speculation, cer-

tainty, probabilities, stable, a quantum jump, to urge, exchange, to

encourage, to earn the respect

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

TEXT: «NIELS BOHR AND QUANTUM MECHANICS»

Niels Bohr (1885-1962), a Danish physicist, was one of the greatest and most influential scientists of the twentieth century. Bohr developed basic ideas about the structure of an atom. These ideas have been widely accepted by scientists ever since. For his important work, Bohr was awarded the Nobel Prize in physics in 1922. Bohr, along with other distinguished physicists of the early 1900’s, developed a new branch of physics known as quantum mechanics. These physicists recognized that the laws of motion and gravity formulated by Sir Isaac Newton in the 1600’s (called the Newtonian laws) could not properly explain motion at the atomic level. Newton had developed his physics with the movements of planets in mind. Early atomic researchers – scientists such as Ernest Rutherford and J.J.Thomson – had thought of atoms as tiny models of the solar system. As physicists probed deeper into the atom, however, they gradually realized that the solar system was not an accurate model for atomic motion. Albert Einstein, Max Planck, Niels Bohr, and others developed the theories of quantum mechanics in the early 1900’s to better describe the atom and its motion. Several important ideas emerged. One idea is that radiation – such as light – is emitted in a stream of separate bundles of energy called quanta. This principle can also be applied to atomic radiation, such as that of electrons. These speculations led physicists to conclude that atomic particles, such as electrons, have properties of both particles and waves. This idea came to be known as the «wave-particle duality» principle. It revolutionized physics. No longer could scientists calculate with certainty the position of an electron in its orbit at a particular moment. Such movements, according to quantum mechanics, can be mathematically described only as probabilities. In other words, since a particle, such as an electron, has qualities of both a particle and a wave, the traditional ewtonian laws of bodies in motion do not apply to it. Niels Bohr developed these ideas further. He claimed that an atom exists in a series of stable states. Between such states, a jump in energy level – a «quantum jump» – occurs in the atom. The jump can be to a higher energy level (increase) or to a lower energy level (decrease). Such a change in energy happens in a fraction of time. With every quantum jump, light photons are given off. Photons are quanta – tiny bundles – of light energy. Bohr based this theory on observations of the spectrum of light that the element hydrogen gives off. Every chemical element gives off a unique spectrum – that is, band of light frequencies. Bohr thought that the band of light frequencies given off by a chemical element could only be explained by the theory of «quantum jumps» of energy in the atom. Scientific observations made during and after his lifetime have proved his theory true. Niels Bohr strongly influenced the physicists and scientists of his time. The reasons for this influence went beyond Bohr’s own contributions to physics. In 1921 the University of Copenhagen opened a new Institute of Theoretic Physics with Niels Bohr as its director. This institute became the world center for exchange of ideas among physicists. The institute owed much of its success and influence to its director. Bohr was a scientist who welcomed the exchange of ideas. He also formed close friendships with his co-workers and encouraged them in their work. In his own country as well as abroad, Niels Bohr earned the respect of fellow scientists. He served as president of the Royal Danish Academy from 1939 until his death in 1962.