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Guglielmo Marconi, an Italian, invented a microphone that
changed sound waves into electronic signals, and then he
developed a receiver that turned them back into sound again. He
also found a way to keep waves of the same length together and
keep those of different wave lengths separate. On his
equipment, a radio wave looked like a letter "s" lying on its
side. Short waves curved up and down more times each second
than longer ones, so he divided all the waves by how many
times they curved each second or by how frequently they
curved. He called each group a frequency. The numbers on your
radio dial are different frequencies. Different stations can
broadcast their programs at the same time using different
frequencies.
Later, scientists found that by using only the top half of a
radio wave they could reduce static and other noise that
interfered with clear sound. This kind of radio transmission is
called FM broadcasting because the frequency has been
modulated or changed.
IV. Comprehension Check.
1. Match the words with their meanings placing a proper
letter on each blank.
_1. microphone a. an .apparatus which
changes radio waves into sounds
_2. to invent b. the metal in the form of
thread
_3. receiver c. having a magnetic force
produced by an electric current
_4. curse d. an instrument that receives
sounds and changes
sounds into electrical energy
_5. to discover e. to find something for the first time
_6. electromagnetic f. to make or produce something
for the first time
_7. wire g. a line of which no part is
straight and which contains no
angles
2. Complete the following sentences with the words from
the box.
broadcast, microphone, curve, machine, sound
signals, receiver, radio transmission, static, noise
a. A transmitter is a__________________.
b. Radio waves carry_________________.
c. A________changes sound waves into electronic sygnals.
d. A________changes signals into sound again.
e. A frequency means the number of times that radio
waves_______per second.
f. Radio stations________their programs.
g. FM means_________
h. In FM radio,_________and_______are reduced.
3. Read the text again to decide if the statements are true
or false. Correct the false ones with the facts from the text.
1. Radio waves carry sounds.
2. "Frequency" refers to the number of times a radio wave
travels.
3. Different radio stations use different frequencies.
4. Some radio waves are shorter then others.
5. It was Guglielmo Marconi who first discovered radio waves.
6. "Wavelength" refers to the length of a radio wave.
7. Unlike telephone messages, radio waves can travel only
short distances.
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