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2. Make up a plan of the text in the form of questions. Text c

1.Mind the following words:

  1. aircraft detection and location – виявлення та місцезнаходження літаків

  2. multicavity magnetron – багатогніздний магнетрон

  3. impetus – поштовх

  4. disclosure – демаскування

  5. warning system – система оповіщення

  6. anti-aircraft gun-laying radar – зенітний радар

  7. anti-submarine radar – проти підводний радар

  8. bomber targeting radar – проти бомбардувальний радар

  9. hamper – закритий

  10. entanglement – захльостування

2. Listen to the text “Radar” and try to understand it.

3. Answer the following questions:

1. What were the British and Germans concentrated on before World War II?

2. What invention gave impetus to the development of radar systems?

3. What happened in 1940?

4. What kinds of radars did Radiation Laboratory developed?

5. Did the Germans produce short wavelength systems??

Unit 9 text a Radio Waves

1.Read and memorize the following words and word-combinations and their translations

  1. Propagation – поширення;

  2. Surface – поверхня;

  3. Curvature – вигіб;

  4. Skywards – до неба;

  5. On striking the Earth – при зіткненні з поверхнею землі;

  6. Refract – заломлювати проміння;

  7. Earthwards – до землі;

  8. Attenuate –розріджений, розріджувати;

  9. Range – діапазон.

  1. Read and translate the following text.

Radio waves from a transmitting aerial can travel in one or more of three different ways.

Surface or ground wave This travels along the ground, following the curvature of the earth’s surface. Its range is limited mainly by the extent to which energy is absorbed from it by the ground. Poor conductors, such as sand, absorb more strongly than water and the higher the frequency the greater the absorption. The range is about 1500km at low frequencies (long waves).

Sky wave It travels skywards and if it is below a certain critical frequency is returned to earth by the ionosphere. This consists of layers of air molecules stretching from about 80km above the earth to 500km. On striking the earth, the sky wave bounces back to the ionosphere where it is again gradually refracted and returned earthwards as if by “reflection”. This continues until it is completely attenuated.

The critical frequency varies with the time of day and the seasons. Sky waves of high frequencies can travel thousands of kilometers but at VHF and above they usually pass through the ionosphere into outer space.

Space Wave For VHF, UHF and microwave signals, only the space wave, giving line of sight transmission, is effective. A range of up to 150km is possible on earth if the transmitting aerial is on high ground and there are no intervening obstacles such as hills, buildings or trees. Space waves are also used for satellite communications.

3. Translate the following word-combinations and memorize them.

Earth’s surface, poor conductor, low frequency, long wave, critical frequency, outer space, sky wave, satellite communication, space wave.

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