2020-05-11
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1. Radar is a system that uses radio waves for detecting and mapping objects.
2. A transmitter emits radio waves which are reflected by the target and detected by a receiver in the different location as the transmitter.
3. The term RADAR was coined in 1947.
4. A radar system emits powerful pulses of radio waves and listens for any echoes.
5. By analyzing the received signal, the reflector can be located and sometimes identified.
6. Although radio waves can be easily generated at any desired strength, the amplitude of the signal returned is usually very large.
7. Radio waves can’t propagate through clouds, fog, or smoke.
IX. Translate from Russian into English
1. Радиоволны, испускаемые передатчиком, отражаются целью и обнаруживаются приемником.
2. Возвращаемый радиосигнал обычно очень слаб.
3. Радар используется в метеорологии, дорожной полицией для определения скорости движения транспорта, в авиации, а также вооруженными силами.
4. Анализируя отраженный сигнал, можно определить местонахождение
отражателя.
5. Радиосигналы могут быть легко обнаружены и усилены во много раз.
Unit 7. Television broadcasting
Active Vocabulary
sophisticated сложный
live transmission прямая передача
picture scanner анализатор изображения
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value величина, значение
photosensitive cell фоточувствительный элемент
to trace out a line размечать строку
frame frequency частота кадра
crude незрелый
scanning speed скорость развертки
to retain an image сохранять изображение
succession последовательность
uninterrupted flow непрерывный поток
to glow светиться
to strike (struck) ударять
allocated dot нужная точка.
I. Read and translated the text
Television. How does it work?
The principles of television aren't as complicated — or as modern — as you might think. TV technology has become more sophisticated than ever, but the basic method of sending a television picture is quite simple.
The first live transmission was made by John Logie Baird, the TV pioneer, in 1924. Television had come a long way since 1884, when Paul Nipkow from Germany patented a mechanical picture scanner. This system formed the basis for Baird's historic, transmissions.
Nipkow's invention depended on a rotating disc. Light passing through the holes on the disc was transformed into electric values by photosensitive cells. The path of each hole in the disc was different, and thus traced out a different line, and read the entire frame in a logical order. At the receiving end, a lamp was used to send out corresponding impulses of light, which then passed through a further rotating disc, identical to the one at the transmitting end, and synchronized with it. The light passing through the disc was projected onto a screen to recreate the original object.
These attempts at televising objects were very crude, because the scanning speed was slow. A comparable system is used today except that electronic scanning equipment is much faster. Approximately 25 frames per second are scanned. Frame frequency is important in allowing television– and films to create moving pictures. The eye retains an image for about 1/16-th of a second, so the mind experiences this succession of pictures as an uninterrupted flow. The large number of lines on modern television make clearly defined pictures possible.
The cathode-ray tube patented in 1897 is used, in its refined form, in present-day television sets. Its importance lies in its capacity to produce pictures. The tube has a screen which glows when struck by a stream of electrons from an electron gun inside the tube. Each point of the screen emits more or less light according to how long the beam is aimed at it.
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A color television has three electron guns — one for each of the primary colors, red, blue and green. They bombard a screen of phosphor dots, arranged in groups of three — one dot for each color — while a masking device sorts the beams so each one falls on its allocated dot. A color television camera also has three cathode tubes and electron guns.
Notes
1.to recreate the original object — для воссоздания исходного объекта
2.the mind experiences — мозг воспринимает
3.in its refined form — в усовершенствованном виде
4.how long the beam is aimed at it – как долго луч направлен на нее
II. Answer the following questions:
1. Are the principles of television complicated? 2. When was the first live transmission made? 3. What did Nipkow's invention depend on? 4. How was light transformed into electric values? 5. Was the light projected onto a screen to recreate the original object? 6. What does the importance of cathode-ray tube lie in? 7. How many electron guns does a colour television have?
III. Look through the text again and try to speak about the frame frequency used in television.
IV. Read the text carefully and find the information about the advantages of digital television:
