Прочитайте текст и выполните задания. A Radar System 1. A radar system has a transmitter that emits ...: ответ на тест 884774 - Английский язык

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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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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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Radio Systems
1. Radio systems used for communications will have the following elements. With more than 100 years of development, each process is implemented by a wide range of methods, specialized for different communications purposes. Each system contains a transmitter. This consists of a source of electrical energy, producing alternating current of a desired frequency of oscillation. The transmitter contains a system to modulate some property of the energy produced to impress a signal on it.
2. This modulation might be as simple as turning the energy on and off, or altering more subtle properties such as amplitude, frequency, phase, or combinations of these properties. The transmitter sends the modulated electrical energy to a tuned resonant antenna; this structure converts the rapidly changing alternating current into an electromagnetic wave that can move through free space.
3. The electromagnetic wave is intercepted by a tuned receiving antenna; this structure captures some of the energy of the wave and returns it to the form of oscillating electrical currents. At the receiver, these currents are demodulated, which is conversion to a usable signal form by a detector sub-system. The receiver is «tuned» to respond preferentially to the desired signals, and reject undesired signals.
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A Satellite Telephone
1. A satellite telephone, satellite phone, or satphone is a type of mobile phone that connects to orbiting satellites instead of terrestrial cell sites. They provide similar functionality to terrestrial mobile telephones: voice, short messaging service and low-bandwidth Internet access are supported through most systems. Depending on the architecture of a particular system, coverage may include the entire Earth, or only specific regions. The mobile equipment, also known as a terminal, varies widely.
2. Early satellite phone handsets had a size and weight comparable to that of a late-1980s or early-1990s mobile phone, but usually with a large retractable antenna. More recent satellite phones are similar in size to a regular mobile phone while some prototype satellite phones have no distinguishable difference from an ordinary smartphone. Satphones are popular on expeditions into remote areas where terrestrial cellular service is unavailable.
3. Since satellite phones are purpose-built for one particular network and cannot be switched to other networks, the price of handsets varies with network performance. If a satellite phone provider encounters trouble with its network, handset prices will fall, then increase once new satellites are launched. Similarly, handset prices will increase when calling rates are reduced.
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The Law and the Family
1. Beyond the mere function of providing a new generation of children, the family is often promoted for its moral contribution to society. Despite a growing labor shortage, the Japanese government has passed very little legislation challenging the assumption that mothers should stay at home rather than go out to work. In Ireland, which is strongly influenced by the doctrines of the Catholic Church, divorce remains illegal.
2. In some societies the family is thought to be so important that there is very little legal intervention in family life. In many Islamic countries, for example, fathers, brothers and sons are allowed considerable authority over the females in their family. As late as the 1970s, the male head of the household in Switzerland was deemed to represent the interests of everyone within that household, and, consequently, none of the women could vote in national elections.
3. But in many parts of the world, the law now promotes the rights of individuals within the family unit, and regulates family relations through legislation. Raised from the taxes of the working population as a whole, child benefit is paid directly to the mother, and retirement pensions are paid to grandparents, so that they are less dependent upon financial support from a family member. In Sweden, parents can be prosecuted for physically punishing their children and children have a limited capacity to divorce their parents. In Britain, as in many countries, there are special family courts with very strong powers to control and transfer private property in the interests of children. Much of the work of other courts is also directly relevant to family life.
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International Law
1. The legal process that concerns relations among nations is called international law. International law serves the international community; international law is about the relations between independent states. It treats them as equals, whatever their population, wealth and power. International law aims at stability in international life and the encouragement of trade and other contacts between states.
2. International law is almost wholly based on custom. The precedents on which it rests are the acts of independent governments in their relations with one another, including treaties and conventions. Behind many of its rules is only a moral sanction: the public opinion of the civilized world. When treaties or conventions are involved, however, machinery to enforce them exists – either an arbitration or conciliation procedure or the submission of the dispute to a regional or international court.
3. A body of rules and principles is observed or at least acknowledged in international relations. These rules concern such matters as territorial titles and boundaries, use of the high seas, limits on war, telecommunication, diplomatic and consular exchange, and use of air space. The major sources of international law on these matters are multilateral treaties, international custom, and such general principles recognized by civilized nations. The United Nations is one of the primary mechanisms that articulate and create international law. The General Assembly and other agencies of the UN bring a combination of diplomacy, negotiation and propaganda to bear on world affairs in ways that produce effective international treaties and affect world opinion. Certain courts also have indirect impact, including the International Court of Justice. Domestic courts in various nations at times also engage in the articulation of international law.
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