1. What is the text about? 2. What is the metric or decimal system? 3. How is the reduction of a quantity to a higher, or a lower one effected? 4. What terms were used for weights and lengths previously to the introduction of the metric system? 5. What standard of length did the French Academy of Science recommend in 1791? 6. What became the standard metre? 7. How was the standard of mass defined? 8. How did the term metre appear? 9. How was called one cubic centimtre of water? 10. What does the word kilometre mean in Greek?
Exercise 3 Translate and memorize the following expressions from the text.
International system of measures and weights, universally adopted, multiply by ten, units of mass, each unit being a multiple of the next lower unit, is effected by, number of places required, to move the decimal point to the left or right, hundreds of different weights and lengths, serious difficulties, among various countries standard of length, one ten-millionth part, along the meridian, to take pains, representatives of various countries, a length equal to, maximum density.
Exercise 4 Find synonyms among the following words.
Along (adv), previously (adv), distance (n), set (v), appoint (v), realize (v), agree (v), define (v), convenient (adj), simple (adj), demical (adj), purpose (n), introduction (n), relationship (n), mass (n), alonside (adv), formerly (adv), weight (n), interrelation (n), inculcation (n), aim (n), metric (adj), ordinary (adj), comfortable (adj), determine (v), come to understanding (v), carry out (v), prescribe (v), fix (v), way (n).
Exercise 5 Write a summary of the text, presenting the content of each paragraph in 2-3 sentences. Use the expressions:
The main idea of the text is The text deals with the one of the most important (urgent) issues Much attention (consideration) is given to (classification, description) It focuses on the matter of The text gives an overview of The text is mainly concerned with The aim of the survey is to show (demonstrate, find) Particular emphasis is given to the analysis of The text gives a detailed analysis of (reports on) To sum up In conclusion
16/3c
Exercise 1 Read the text and translate it in written form.
Radar
(1) The word radar means Radio Determination and Ranging. Radar equipment is capable of determining by radio echoes the presence of objects, their direction, range and recognizing their character.
(2) There are several types of radar sets, all of them consisting of six essential components, namely: a transmitter, a receiver, an antenna system, an indicator(s), a timer, and, of course, a power supply.
(3) A radar set detects objects by sending out short powerful pulses of ultra-high frequency radio wave energy from a high power transmitter. The directional antenna takes this energy from the transmitter and radiates it into beam (similar to that of a searchlight).
|
|
|
(4) As the transmitted energy strikes an object, a portion of it is reflected back. The receiver picks up the returning echo through its antenna and translates it into visual readable signals on a fluorescent screen. The appearance of these signals shows the presence of an object within the field of view of radar.
(5) The electron beam sweeps across the face of a clock. Just as the hand of a clock completes its sweep in sixty seconds, the electron can be made to travel across any desired portion of the screen in some predetermined interval of time. It is the timer, which is the synchronizer of the whole system, which times the transmitter pulse and the indicator. The use of this timed pulses and the fact that the radio waves travel at the constant velocity of light gives a simple means of measuring range. The accuracy with which time is measured determines the accuracy of the range.
(6) How then is the direction in which an object lies to be found? Both azimuth and elevation can be determined by means of the directional antenna. The antenna may be rotated as the pulses are sent out and the strongest signal appears on the screen when the antenna points directly at the object. The direction of the antenna enables the determination of azimuth and elevation. Thus, with the help of a radar set we can get a three-dimensional location of an object.
(7) The wide use of radar sets in our everyday life will make air and sea entirely safe. Radars may be installed on every ship at sea as well as in every large harbour. They will prevent collisions in fog and aid a ship to sail safely into any harbour, regardless of night or weather. Similarly airplanes will be able to fly over mountain ranges in storms and effect blind landing during poor visibility.
