8. Choose the appropriate form of the verb:

a) Radio engineering (penetrates, will penetrate, has penetrated) into the national economy, science, industry.

b) One of the most important applications of radio engineering (involve, involves, involved) long-distance communication.

c) Radio engineering equipment (provide, will provide, provides) for stable round-the-clock communication with marine vessels, aircraft and spaceships.

d) Radio engineering systems (enables, will enable, enable) us to effect interplanetary communication.

e) New sciences (have been born, has been born, will be born) such as radio physics, radio astronomy, etc.

f) Radio techniques and methods (is widely used, was widely used, are widely used) in experimental physics.

g) The extensive use of radio methods (gives, have given, has given) rise both to radio engineering and electronics.

h) Radio electronic equipment (uses, will use, is widely used) in medicine.

i) Cybernetic systems (were playing, play, will play) a decisive part in automation.

j) Television (will cover, has covered, covers) steadily expanding regions in many parts of the globe.

Lesson Two

I. Pre-text exercises.

1. Learn the meaning and pronunciation of the following words:

angle ['æŋgl], remain [ri'mein], property ['prɔpəti], polarization [poulərai'zeiŋn], alternating ['ɔ:ltə:neitiŋ], abbreviate [ə'bri:vieit], mutually ['mju:tjuəli], reverse [r'ivə:s].

2. Read and remember the Plural of the following Nouns:

radius ['reidiəs] – radii ['reidiai]

datum ['deitəm] – data ['deitə]

formula [' fɔ:mjulə] - formulae ['fo:mjuli]

index ['indeks] - indices ['indisi:z]

II. Read the following text carefully. While vou are reading look for the answers to the questions:

1. What are the essential properties of radio waves?

2. What's the wave front?

3. When is the wave vertically or horizontally polarized?

Text b Radio Waves

1. Electrical energy that has escaped into free space exists in the form of electromagnetic waves. These waves, which are commonly called radio waves, travel with the velocity of light and consist of magnetic and electrostatic fields at right angles to each other and also at right angles to the direction of travel.

2. One half of the electrical energy contained in the wave exists in the form of electrostatic energy, while the remaining half is in the form of magnetic energy.

3. The essential properties of a radio wave are the frequency, intensity, direction of travel, and plane of polarization. The radio waves produced by an alternating current will vary in intensity with the frequency of the current and will therefore be alternately positive and negative.

4. The distance occupied by one complete cycle of such an alternating wave is equal to the velocity of the wave divided by the number of cycles that are sent out each second and is called the wave length.

5. The relation between wave length X in meters and frequency in cycles per second is therefore

The quantity 300 000 000 is the velocity of light in meters per second. The frequency is ordinary expressed in kilocycles, abbreviated KC; or in megacycles, abbreviated MC. A low-frequency wave has a long wave length while a high frequency corresponds to a short wave length.

6. The strength of a radio wave is measured in terms of the voltage stress produced in space by the electrostatic field of the wave and is usually expressed in microvolts stress per meter.

7. A plane parallel to the mutually perpendicular lines of electrostatic and electromagnetic flux is called the wave front.

8. The wave always travels in a direction at right angles to the wave front, but whether it goes forward or backward depends upon the relative direction of the lines of electromagnetic or electrostatic flux.

9. If the direction of either the magnetic or electrostatic flux is reversed, the direction of travel is reversed; but reversing both sets of flux has no effect.

10. The direction of the electrostatic lines of flux is called the direction of polarization of the wave. If the electrostatic flux lines are vertical the wave is vertically polarized; when the electrostatic flux lines are horizontal and the electromagnetic flux lines are vertical, the wave is horizontally polarized.