UNIT 11

 

V. 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.

 

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

 

1. быстро-движущиеся электроны _______________________________
2. передающие антенны ________________________________________
3. вибрировать с одинаковой частотой ___________________________
4. поперечные волны ___________________________________________
5. свойства ____________________________________________________
6. ведёт себя как волна _________________________________________
7. корпускулярно-волновой дуализм _____________________________
8. поток частиц ________________________________________________
9. если источник точечный _____________________________________
10. поверхность _________________________________________________
11. обратно пропорциональна квадрату расстояния ________________
12. максимальные и минимальные значения величины напряженности
13. не совпадают _________________________________________________
14. квантовая теория не может объяснить __________________________
15. распространяться с постоянной скоростью _____________________
16. проходит через другие среды __________________________________
17. плотность среды ____________________________________________

 

VII. Find Russian 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 expending 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 transmitted through a medium?
11. What are the other principal properties of electromagnetic radiation?

 

XII. Translate in Russian 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.

 

XIV. Dictation-translation.

 

1. Электромагнитное излучение возникает, когда электроны колеблются, замедляют скорость движения или меняют энергетический уровень в атоме.
2. Радиоволны вырабатываются вращающимися электронами в металле передающих антенн.
3. Электромагнитное излучение состоит из движения волн как в электрическом, так и в магнитном полях, которые вибрируют с одинаковой частотой, но под прямыми углами по направлению к распространению.
4. Таким образом, электромагнитные волны являются примерами поперечных волн.
5. Электромагнитное излучение также обладает свойствами частиц, и его истинная природа остается загадкой.
6. В одних случаях электромагнитное излучение ведет себя как волна, в других – как частица.
7. Этот очевидный корпускулярно-волновой дуализм не был полностью объяснен.
8. С увеличением расстояния от источника, интенсивность излучения уменьшается, в то время как поверхностная площадь сферы увеличивается.
9. Интенсивность излучения обратно пропорциональна квадрату пройденного расстояния.

10. В соответствии с квантовой теорией световая (лучистая) энергия излучается в виде прерывистых «порций энергии», называемых квантами или фотонами.