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problems that gave rise to radar, the term being referred to as a code word for "Radio Detection and Ranging".

High-frequency radio waves are reflected from any surface or sharply defined region* at which there ts a decided"" change from the degree of conductivity or the dielectric constant of the air through which the radio wave is travelling. The fact that short wave radiation is reflected from everything, whose electric properties differ materially " from those of air is made u s e " о f in radar.

In radar an electromagnetic signal is sent out, reflected or re-radiated from the object to be detected, and received at the place where the signal originated.

Radar waves are not sent continuously by the transmitter, but are emitted * in brief" pulses followed by idle" periods. The reflected pulses are picked up " by the receiver during instants in which the transmitter is idle.

Radar operates with frequencies of hundreds of millions of cycles per second, with wavelengths of only a few inches" or centimeters. Such waves are similar to light waves in that they are bound" to travel in straight" lines or in lines of sight from the transmitter. The effective distance of detection and observation is limited by the fact that such waves cannot pass beyond the curvature of the earth which forms the horizon and still be reflected back to a receiver which is near the transmitter.

The emitted pulses travel through space at a speed of about 186,340 miles per second. It follows that measurement of the length of time required for a pulse to go from transmitter to reflecting object and back to the receiver makes it possible to determine the distance travelled by the pulse. Half 2* of the total 22 distance travelled is the distance from the radar apparatus to the reflecting object. It takes23a pulse a little more than one ten-thousandth of 9 second to travel to an object ten miles away and return to the receiver, a duration 2* which makes it possible to get a continuous indication of the object on the screen of a cathode-ray tube *.

Radar was brought Into use25 during World War II to accurately get the range of an enemy ship or plane and to automatically direct gunfire toward the target. Now radar i s largely made use of in peaceful applications. Without going into particulars2e the purpose of radar may be defined as follows 2: to detect the presence of distant 2» objects, to indicate their distance from the apparatus, also their position to the right or to the left; and, if moving, their speed in relation to the position of the radar apparatus.

• fathode-ray tube -электроннолучевая трубка



УПРАЖНЕНИЯ

Грамматические упражнения

1. Переведите предложения, в которых сказуемое выражено несвободными словосочетаниями типа «глагол to Ье+существительиое с предлогом»:

to be in excess «превышать»; to be in progress «происходить, иметь место»; to be in a position «быть в состоянии»; lo be under way «осуществляться, происходить, иметь место»; to be of interest «представлять интерес»

to be in excess (of smth.)

1. The consumption of fuel in a rocltet engine is far in excess of other types of engines.

2. Gases exert on the walls of containers pressures which are far in excess of those that one would expect from the weight of the gas.

3. The control mechanism is usually designed so that corrective action is taken only if the deviation * is in excess of the permissible range of error .

to be in progress

4. Systematic observations and recording of meteorological characteristics have been in progress in numerous countries and on ships at sea for many years.

5. Research work and experimental investigations are constantly in progress to find materials with magnetic properties better than those in use.

to be in a position

6. We are now in a position to compare the cost of electricity generated in a nuclear plant with the cost of electricity generated in a conventional thermal station.

7. In some cases it is by the spectroscope that we are in a position to make statements as to the substances present in the stars.

8. So we are now in a position to determine the minimum current or emf detectable by means of a galvanometer.

to be under way

9. The study of space on a large scale with scientific instruments mounted on satellites is under way.

10. The reactor programme which includes all important types of reactors available is now under way.

11. There is also under way a search for new techniques of application of transistors.

• deviation - отклонение

• error -ошибка



to be of interest (value, importance, significance)

12. The orbit of Lunik III is of unusual interest.

13. The "storms" of corpuscular radiation range widely in intensity and it is of considerable importance to any space flight program to consider how dangerous they are.

14. As compared to an ordinary nuclear power plant, electrical-power-generating nuclear plant is likely to be of even greater significance in astronautics.

2. Переведите предложения, в состав которых входят несвободные словосочетания типа «глагол to come (to go)-f существительное с предлогом»:

to come into use «начинать применяться»; to come into action, to come Into play «вступать в действие»; to come into being «возникать»; to go Into play «вступать в действие»; to go into service «начинать применяться»; to go into particulars «вдаваться в подробности»

to come into use, to come into action, to come into play, to come into being

1. A nuclear reactor will be practical at some future time when very large long-life space vehicles come into use.

2. When flying in the upper atmosphere new forces come into action.

3. The temperature on a planet that possesses an appreciable atmosphere cannot be easily calculated, because complex meteorological effect come into play.

4. We cannot say with certainty how the solar system had come into being.

5. In order to investigate how these new particles come into being, one must first study a very remarkable phenomena, the transformation of a photon of high energy into a pair of oppositely charged electrons.

to go into play, to go into service, to go into particulars

6. When speaking of momentum (the mathematical product of the velocity and the mass of an object), Newtons third law of motion goes into play.

7. A new radar recently went into service.

8. Here we shall not go into particulars as to modern trends in radio navigation technique.

3. Переведите предложения, содержащие несвободные словосочетания типа «глагол to bring (to put, to set)-f существительное с предлогом»:

to bring into action «начинать действовать»; to bring into use «начинать применяться»; to put into use «вступать в действие»; to put Into operation «вводить в строй»; to put into practice «начинать применяться»; to set into motion «приводить в движение»

to bring into action, to bring into use

1. When the rocket approaches the Moon new gravitational forces brought into action, that of the Moon.

2. Originally, rddio was brought into use to communicate with ships at seq.



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