UNIT 10

 

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

 

spectrum (spectra), wavelength, frequency, microwave, infrared radiation, ultraviolet radiation, to comprise, apart from, visible, to be detected, application, to emit, a source of energy, a dual wave/particle nature, to traverse, to travel, to penetrate, transparent, current, cell, retina

 

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

 

Text: “Radiant Energy”.

 

Energy may take various forms – sound, chemical, and electrical energy, for example. One whole range of related forms is known as radiant energy or electromagnetic radiation. Together they make up the electromagnetic spectrum, whose various radiations are characterized by particular ranges of wavelengths and frequencies. At the long-wavelength, low-frequency end of the spectrum are radio waves, followed by microwaves and infrared radiation. Then comes visible light and ultraviolet radiation, and the shortest wavelengths and highest frequencies comprise X rays and gamma rays.

Apart from light, all forms are invisible to the human eye, although many can be detected by electronic devices and special types of photographic film. Almost all have found practical applications: in radio communications and radar, infrared and microwave heating, photography and spectrographic analysis, and medical and industrial radiology. The most important forms of electromagnetic radiation are visible light and infrared radiation (both of which are emitted by the sun, our principal natural source of radiant energy). Without them, life would be impossible.

Nature and properties of radiant energy. The various forms of radiant energy have many common characteristics, the most fundamental of which concerns their nature. They are all wave motion, consisting of varying electric and magnetic fields, but they can also be considered as being made up of "particles," or quanta, of energy called photons. Radiant energy therefore has a dual wave/particle nature.

In theory it is possible to explain all the effects and properties exhibited by radiant energy in terms of both wave motion and photons. But in practice it is usually more convenient to employ whichever of the two concepts explains a particular effect most easily.

Another basic characteristic of electromagnetic radiation is the fact that it does not need a medium in which to travel, and so it can traverse the vast emptiness of space. But the various forms of radiation can also travel through other mediums: light travels through air, water, and glass, for example, and X rays and gamma rays can penetrate body tissues and even pass through metal; that is to say, even a metal is “transparent” to X rays and gamma rays.

In a vacuum, all forms of electromagnetic radiation travel at the same constant velocity – called the speed of light. In other transparent mediums, they travel more slowly, the velocity depending on the wavelength of the radiation and, generally, on the density of the medium. In other mediums, different wavelengths travel at slightly different velocities; the longer the wavelength, the faster the radiation travels. So in the case of visible light, red light travels faster than blue light in any particular transparent medium does.

The various types of radiant energy have different wavelengths and frequencies. These two characteristics multiplied by the frequency are equal to the velocity. Because the velocity is constant in any particular medium, wavelength and frequency are inversely proportional to each other; the longer the wavelength, the lower the frequency is, and vice versa.

Effects of radiant energy. Radiant energy can be detected only when it is absorbed and brings about an observable effect—usually by causing a physical or chemical change. Gamma rays ionize certain gases when absorbed by their molecules. X rays and visible light cause chemical changes in a photographic emulsion that darken it when it is developed. Ultraviolet radiation causes substances such as fluorite to fluoresce (emit light). Visible light stimulates the nerve cells in the retina of the eye, thereby making vision possible.

 

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 Russian 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 Russian.

 

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 _________________________________________________

 

VIII. Find English equivalents in the text.

 

1. ряд, линия ___________________________________________________
2. заключать в себе, охватывать __________________________________
3. могут быть найдены __________________________________________
4. практические применения _____________________________________
5. природный источник _________________________________________
6. двойственное происхождение __________________________________
7. среда ________________________________________________________
8. пересекать огромную пустоту пространства _____________________
9. проходить через воздух _______________________________________
10. прозрачный _________________________________________________
11. плотность среды _____________________________________________
12. экспериментально измеренное значение ________________________
13. постоянный _________________________________________________
14. обратно пропорциональный __________________________________
15. физическое или химическое изменение ________________________

 

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 made 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.  

 

XV. Dictation-translation.

 

1. Энергия может быть различных форм, например: звук, электроэнергия и др.
2. Самыми важными формами электромагнитного излучения являются видимый свет и инфракрасное излучение; без них жизнь была бы невозможна.
3. Различные формы лучистой энергии имеют много общих свойств.
4. Теоретически возможно объяснить все свойства лучистой энергии с помощью понятий «волновое движение» и «фотон».
5. Волновое движение – это одна из форм радиоактивной энергии.
6. Электромагнитная радиация может пересекать пространство.
7. Только радио волны, инфракрасное и ультрафиолетовое излучение может проникать внутрь земной атмосферы.
8. Различные формы излучения могут проходить через другую среду.
9. Свет проходит через воздух, воду, стекло.
10. Рентгеновские лучи могут проходить сквозь ткани человеческого тела и даже через металл.