Чтение общенаучной литературы. Кытманова О.А. - 35 стр.

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36
others) have to travel to find the right spot and then set up the cameras,
microphones, and other equipment needed to make the film. A crew might spend a
whole day getting only a few minutes of film. In the case of a "live" outside
broadcast, the director and his crew are linked to the studio control room by special
"land lines".
Computers now play a large part in presenting and "processing" the images that
we see on our television screens. They are particularly valuable in generating, or
producing, "graphics", or pictures.
Radio Programs. Studio broadcasts are prepared, produced, and directed in much
the same way as television programs, except that no pictures are transmitted. In
radio programs, the microphone is the camera, as it were, but apart from this
distinction, many of the same procedures apply. For example, a production
assistant keeps a check on running times, tape-recorded material has to be inserted
at the appropriate spot, tape recording needs to be edited to fit the correct time
period, and so on.
Modern radio broadcasting has come to accept the principle of having no silences
in transmissions. On pop-music stations where programs consist mainly of "disk
jockeys'* playing records and talking in between them, any gaps can easily be
filled. On channels specializing in speech, drama, or news, a continuity announcer
provides links between programs and is on hand to fill up any awkward gaps
caused by technical problems.
The world of broadcasting is more than ever a world of fascinating and varied
sounds and visual images. It is a world that could not have been imagined in 1901.
when Marconi made his first transatlantic transmission in Morse code.
RADAR
RADAR is an electronic system for locating distant objects. It works by sending
out radio waves from an antenna in a thin beam of very short pulses and listening
for echoes to return to the antenna. (For an explanation of radio waves, see under
RADIO.) By measuring the time a single pulse of energy takes to return to the
antenna (the speed of radio waves is 300,000 kilometers or 186,000 miles a
second) it is possible to work out the distance the pulse traveled. If the direction of
the pulse is known, then the combination of distance ("range") and direction
("bearing") gives the position of the object (known as a "target") which caused the
reflection of the pulse. A rotating radar-reflecting antenna sweeps out a circle with
its microwave radar beam. Clearly, a process like this which works just as well at
night or in fog is very useful for detecting aircraft and ships. If the radar is fitted to
an aircraft, it can be used to detect high ground. If it is on a ship, it can locate land
and other ships. These are the most common uses for radar, but an enormous
number of other uses have been found.

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