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Heinrich Hertz. ВАРИАНТ 4. Modulation
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Heinrich Hertz
1. One of the most brilliant experimentators in the history of natural science is a German physicist Heinrich Hertz (1857 – 1894).
2. Deeply convinced of the truth of the Faraday – Maxwell theory, he set himself the task of proving experimentally the existence of free electromagnetic waves. He established the fact that they are governed by the same laws (reflection, refraction and polarization) as light waves. When Hertz had proved the identity of the properties of electromagnetic waves and light, he could control them as well.
3. But nevertheless, these Hertzian waves did not go farther than his laboratory or the University garden in Bonn. His apparatus was not very sensitive for an experiment with greater distances and not suitable at all for experiments aimed at a practical transmission of signals over considerable distances. The scientific value of Hertz’s discovery, however, is not less though he did not find a practical application for it.
4. Hertz’s discovery was immediately recognized throughout the world, and Popov was one of the first to begin elaborating1 further this extremely important scientific advancement. He read papers2 and delivered public lectures, always pointing out that this new achievement of science is not only of theoretical value, that it may find a practical application.
5. The path to Popov’s great discovery was marked by the investigations of many scientists in different countries.
Пояснения к тексту:
1. elaborate – разрабатывать
2. read papers – выступать с докладами
Задание 8. Выпишите из текста предложения, содержащие наиболее полный ответ на поставленный вопрос.
What did Popov do to make Hertz’s discovery popular?
ВАРИАНТ 4
Задание 1. Перепишите предложения и переведите их, принимая во внимание различные функции слов it, that, one.
1. It is cheaper to transmit a low current at a high voltage, rather than a high current at a low voltage.
2. It was only in the past century that man understood the nature of heat.
3. One should be careful when working with chemical substances.
Задание 2. Перепишите следующие предложения и переведите их, учитывая особенности перевода на русский язык определений, выраженных именами существительными.
1. The radio speaker is similar to the telephone receiver.
2. The ionosphere layers reflect the radio waves.
Задание 3. Перепишите предложения, определите в каждом из них глагол-сказуемое, его видовременную форму и залог. Переведите предложения на русский язык.
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1. A new research is being carried out successfully.
2. They have been obtained very interesting data.
Задание 4. Перепишите предложения, подчеркните причастие, определите его форму, функцию и переведите предложения на русский язык.
1. The cloud of electrons formed in the space between the cathode and the plate is called the space charge.
2. The simplest combination of elements constituting an electron tube is a diode.
Задание 5. Перепишите предложения, подчеркните герундий, определите его функцию и переведите предложения на русский язык.
1. The way of connecting these wires was described earlier.
2. Measuring temperature is necessary in many experiments.
Задание 6. Перепишите предложения, определите, является ли инфинитив подлежащим или обстоятельством цели, переведите предложения на русский язык.
1. To obtain vacuum in a valve gas should be removed from it.
2. To detect distribution of alpha particles in the foil required sophisticated experimental method.
Задание 7. Прочтите и устно переведите текст, затем перепишите и письменно переведите 1-й абзац текста.
Modulation
1. To sent information from transmitter to receiver the wave called the carrier, must be varied in accordance with the information to be transmitted. The process is termed “modulation” and the information that is being transmitted is termed “the modulating signal”. The modulation takes place whenever a carrier wave is affected by signal which is to be transmitted. For example, the frequencies and amplitudes of sound waves are modulated by the speech information which is transmitted from person to person. The two most important methods are amplitude modulation and frequency modulation.
2. Amplitude modulation is known to be widely used in radio broadcasting and radio telephony. In an amplitude modulation system, the amplitude of the transmitted carrier is made to be instantly proportional to the amplitude of the modulating signal. Modulation can be sinusoidal, square or any other shape which it is necessary to transmit. The modulator is the device which produces at the output the signal to be transmitted.
3. If the carrier is modulated a 400 Hz sine wave then the receiver will receive a carrier signal the amplitude of which is varying at 400 Hz and variations will be sinusoidal. The 400 Hz modulation frequency may be replaced by a speech waveform1, in this case the carrier will now be amplitude modulated so as to2 correspond with a speech signal. This system is widely used: for example, for broadcast on the long and medium wavebands.
Пояснения к тексту:
1. speech waveform – речевой сигнал
2. so as to – чтобы
Задание 8. Выпишите из текста предложения, содержащие наиболее полный ответ на поставленный вопрос.
Where is the amplitude modulation widely used?
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