XIV. Put the questions to the following sentences:
1. Radio is a special kind of long-distance communication. 2. Currents with frequency of thousands of cycles are called high frequency currents. 3. The very first apparatus for radio communication was called wireless telegraph or wireless telephone. 4. In the modern world radio and television play an important role as a mass media of information. 5. Our television is linked up with the Intervision and Eurovision international systems. 6. The science of radio astronomy was born only about thirty years ago. 7. Gamma rays are still shorter with a wavelength of about one-ten-thousand-millionth part of an inch. 8. See-while-you-talk communication service is the future of telephone communication.
XV. Choose the correct form of the verb.
1. We know the electric current to flow \flew in metal parts. 2. The engineer wants the new devices tested\ to be tested in the laboratory. 3. We know radio to play\ is played a great part in human life. 4. Radio allows us to communicate\ communicated with the remotest corners of the world. 5. Computer science is to regard\to be regarded as anew discipline. 6. An electronic machine has to be used to make\to be made these calculations. 7. The apparatus to assemble\to be assembled is very complicated. 8. The results to receive\ to be received will be published next month.
Lesson Text: Radio Waves
Pre-text exercises
I. Memorize the pronunciation of the following words:
Velocity, angles, electrostatic, polarization, alternating, current, intensity, essential, cycle, equal, length, frequency, flux, backward, polarization, angles.
II. Find the Ukrainian equivalents for the following English words and word combinations:
a) Velocity; angle; frequency ; remain; property; flux;
b) Швидкість; властивість; вугілля; зберігати; у положенні зміни; частота;
III. Read and translate the text: “radio waves”
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. 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. 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. 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. The relation between wave length X in meters and frequency fm 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.
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. A plane parallel to the mutually perpendicular lines of electrostatic and electromagnetic flux is called the wave front. The wave always travels in a direction at right angles to the wave front, but whether in goes forward or backward depends upon the relative direction of the lines of electromagnetic or electrostatic flux. 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. 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.
Post-text exercises
I. Find the Ukrainian equivalents for the following English words and word combinations:
into free space, radio waves, essential properties, direction of travel, wave length, the velocity, relation, distance, the voltage stress, flux, direction, at right angles.
II. Translate into English:
Випромінюється у вільний простір; змінний струм; площина поляризації; короткохвильова довжина; напруга; напрям електростатичних ліній; сила радіохвилі.
III. Fill in the blanks with the following words:
properties, light, magnetic, alternating, velocity
1. Radio waves travel with the …of light. 2. Radio waves consist of ….and electrostatic fields.3. The essential … of a radio wave are the frequency, intensity, direction of travel, and plane of polarization. 4. The quantity 300 000 000 is the velocity of …in meters per second. 5. The radio waves produced by an ….current.
IV. Complete the following sentences, using active vocabulary:
1.Electrical energy that has escaped into free space exists….2.The essential properties of a radio wave are…3.The radio waves produced by….4.The distance occupied by one complete cycle of……5.The strength of a radio wave is measured in…… 6.The direction of the electrostatic lines….
V. Translate the following prepositional word combinations into Ukrainian:
escaped into free space, velocity of light, consist of magnetic fields, direction of travel, plane of polarization, direction of the lines of electromagnetic flux, travels in a direction at right angles, the frequency of the current.
VI. Translate the following definitions and memorize the terms:
Oscillating current. A current that alternately increases and decreases but is not necessarily periodic.
Signal. A visual, audible, or other indication used to convey information.
Automatic system. A system in which the operations are performed by electrically controlled devices without intervention of operators.
Radio channel. A band of frequencies of a width sufficient to permit its use for radio communication.