Вопрос № 223122 - Английский язык

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The principles of 1________________ in a simplified form might be stated as follows:
1. electromagnetic radiation at high radio frequencies is 2________________ to detect and locate remote reflecting objects;
2. the radiation is sent out in pulses of a few microseconds’ duration, separated by intervals many times the duration of each pulse;
3. the pulses are returned from the reflecting objects and the returns are detected and displayed by receiving equipment placed at the point of transmission;
4. 3________________   to the objects is determined by measurement of the time it took the pulses to reach the targets from the transmission equipment and return to it;
5. the directions of the targets are determined by use of highly directive radio 4__________________.

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A Radar System
1. A radar system has a transmitter that emits radio waves called radar signals in predetermined directions. When these come into contact with an object they are usually reflected and/or scattered in many directions. Radar signals are reflected especially well by materials of considerable electrical conductivity – especially by most metals, by seawater, by wet land, and by wetlands. The radar signals that are reflected back towards the transmitter are the desirable ones that make radar work. If the object is moving either closer or farther away, there is a slight change in the frequency of the radio waves, due to the Doppler effect.
2. Radar receivers are usually, but not always, in the same location as the transmitter. Although the reflected radar signals captured by the receiving antenna are usually very weak, these signals can be strengthened by the electronic amplifiers that all radar sets contain. The weak absorption of radio waves by the medium through which it passes is what enables radar sets to detect objects at relatively-long ranges – ranges at which other electromagnetic wavelengths, such as visible light, infrared light, and ultraviolet light, are too strongly attenuated. In particular, there are weather conditions under which radar works well regardless of the weather. Such things as fog, clouds, rain, falling snow, and sleet that block visible light are usually transparent to radio waves.
3. Finally, radar relies on its own transmissions, rather than light from the Sun or the Moon, or from electromagnetic waves emitted by the objects themselves, such as infrared wavelengths (heat). This process of directing artificial radio waves towards objects is called illumination, regardless of the fact that radio waves are completely invisible to the human eye or cameras.
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What enables radio waves to detect objects being far enough from radio transmitter?

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Sonar (Sound Navigation and Ranging) is employed to locate submerged enemy 1________________. Like radar it is an echo-ranging 2__________________. It operates in the following way - a ship 3________________ a sound wave into the water. Encounting an obstacle the wave is reflected back to the ship, which – since the speed of sound through water is known - determines its distance from the object from the time it took the echo to return. To create the original sound wave, the ship generates 4________________ signals in а transmitter; it then sends these to a transducer, positioned on its keel as deeply in the water as possible. The transducer converts the signals into sound and transmits them through the water.

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The 1________________ is basically a three-section device composed of two outside sections and a middle section. The two outside 2______________ are doped so that they are either P- or N-tуре, and the middle section is doped opposite to the outside sections. Transistors are 3_________________ as NPN or PNP according to the doping of the sections or elements. When the two outside sections are N-type 4_________________ and the middle section is a P-type, the transistor is an NPN-type. When the two outside sections are P-types and the middle is N-type, the transistor is a PNP-type.

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Experts believe that some boys are spending so much time playing computer games and watching violent films that they are living in a fantasy world. When girls talk about using home computers, they often discuss different types of software that they use for learning. Boys simply talk about computer games. When 14-year-old girls were asked what they would like to do in the future, they mentioned realistic jobs such as vet, teacher or doctor. The boys' answers were either very vague such as, "I just want to be happy and have lots of money" or unrealistic and they said things such as, "I want to be a fighter pilot”.
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What is the topic of girls’ discussion about using home computers?

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A lot of knowledge is a dangerous thing for addicts of the Internet. Information is becoming the drug of the new century.
The research, conducted among 1000 managers in Britain, America, Europe and the Far East shows that, as information sources such as the Internet and cable news channels proliferate, we are witnessing the rise of a generation of dataholics.
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What are people who use the Internet a lot called?