Questão de Língua Inglesa

Read the text and mark the correct option. The Radar The word RADAR stands for Radio Detection and Ranging. It is a technology which was properly used for the first time during the Second World War by the allied troops against the Germans. Basically, a radar is an anti-collision tool and can measure the bearing and the distance of a selected target. It is therefore a vital aid on ships and airplanes, especially in case of low or blind-visibility navigation. To detect a target’s position, the radar dish or antenna sends out pulses of electromagnetic waves. When these waves hit the target their echo is returned to the aerial and transformed into visual signals shown on a screen called PPI (Plan Position Indicator) or display. The capacity of the antenna to concentrate the irradiation energy in the dish is called gain. The whole process is based on the principle that radio waves bounce off solid surfaces. It is therefore possible to determine the bearings and distances of far away targets and deduce infonnation about potential hazards. The Radar can also be used to find out the position of a ship at sea, but only in the case in which a fix (a fixed point of reference on the land) is available. For this, other more precise, handy and faster tools, like the GPS, are used. (Adapted from: Flash on English for Transport and Logistics)