Intermediate 1
Physics
Telecommunication
Questions
and
Answers
Beath High School - Int 1 Physics
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Intermediate 1
Physics
Telecommunication
Questions 1 to 10
Questions 11 to 20
Questions 21 to 30
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1.
The telephone, telegraph and radio are all forms of
communication systems.
Which of these systems does not need a wire link
between the transmitter and the receiver?
The radio does not need a wire link between the
transmitter and receiver.
This is because the signal (the message) is carried on
invisible radio waves which need no substance to carry
them.
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2. Louise is listening to her radio and enjoying the music
played by Atlantic 252. The signal is transmitted from
a radio mast at the other end of the country.
(a) Describe the signal which travels from the radio
station to the radio receiver.
The transmitter sends out invisible waves of energy
which we call radio waves.
(b) At what speed does the signal travel?
Three hundred million metres per second (300 000 000 m/s)
(c) What is transferred from the radio mast to the
aerial in her radio?
energy
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3. Raymond has drawn a block diagram for a radio but
can only remember the first unit.
aerial
tuner
decoder
amplifier
speaker
Power
supply
(a) Complete the correct block diagram for the radio system.
(b) Describe the function of any three units within the radio
receiver.
Aerial
Tuner
Decoder
Amplifier
Power Supply
Loudspeaker
-
Detects all radio waves.
Selects one radio station.
Separates the sound signal from the radio wave
Makes the small electrical signal stronger.
Supplies extra energy to the amplifier.
Changes the electrical signal into sound.
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4. A radio display shows a combination of letters and
numbers as shown.
FM 102.5 MHz
The numbers tell the listener that the transmitter
sends out 102.5 million waves in a certain time.
How long a time does it take to send out 102.5 million
waves?
The time taken is one second.
(This is because frequency means the number of
waves produced every second.)
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5. Jason is checking the times of the football
broadcasts in his newspaper.
Radio Station
Time
Programme
Radio Clyde 2
2.00 p.m.
“Sportsound”
Westsound
2.00 p.m.
“Sportsound”
The two radio stations broadcast the same
programme at the same time.
However, the signals are not identical.
In what way are the signals different from each
other?
They are carried on two different radio frequencies.
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6. June is listening to a rock concert programme on her
radio while her sister Alison is watching the same
programme on her television.
(a) What type of wave is detected by the radio and
the television set?
Radio waves.
(b) What is the difference between the two waves?
They are different frequencies.
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7. Each television station has a name which we are all
familiar with.
BBC 1;
BBC 2;
Channel 4;
STV;
Channel 5
As well as the name, how can a particular broadcast
station be identified?
It can be identified by its frequency.
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8. A television is an electronic system, which can be
represented by a block diagram, as shown below.
(a) The diagram is incomplete.
Complete the block diagram showing all the parts of a
TV in the correct order.
aerial
tuner
sound
decoder
Vision
decoder
sound
amplifier
Vision
amplifier
speaker
Picture
tube
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8. A television is an electronic system, which can be represented by
a block diagram, as shown below.
(b) Describe the function of any four parts of the TV system.
aerial
- The aerial detects many radio signals and
changes them into electrical signals.
tuner
- The tuner selects the signal you want.
(i.e. the channel of your choice)
sound
decoder
Vision
decoder
- The decoders separate the sound and
vision signals from the carrier wave.
sound
amplifier
Vision
amplifier
- The amplifiers make the electrical
signals stronger.
speaker
Picture
tube
- The loudspeaker changes the audio
signal into a sound wave,
- The picture tube changes the video
signal into pictures.
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9. A television screen is coated with 3 special chemicals which give
out different colours of light energy (red, green and blue).
A viewer switches on the set and sees a yellow screen.
She knows that yellow light is not emitted by the chemicals on
the screen of any TV set.
Explain why the viewer can see a colour on the screen which is
not one of the 3 colours emitted by the chemicals on the screen.
The red and green dots are lit up on the TV screen.
These two colours of light combine to make yellow.
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10. High frequency radio signals are sent from the USA to Britain.
The signals are received by a ground station in Cornwall.
(a) Describe what happens to the signal after it leaves the
American ground station.
It is transmitted up to a satellite in orbit.
There it is amplified and then retransmitted to Cornwall.
(b) Weather forecasters on television show us detailed pictures
of rain clouds over Britain.
How is this kind of information gathered?
A satellite in orbit around the earth takes pictures
and transmits them back to earth.
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11. An army unit on military exercise at the Earth's equator have
positioned a satellite dish as shown.
Aerial
Dish
Aerial
Curved reflector
During their stay they find there is no need to change the
position of the dish, which is pointing vertically upward.
Communications are good and are never interrupted.
(a) Why is there no need to continually alter the position of the
satellite dish?
The satellite stays at the same point above the equator.
(b) What name is given to the type of satellite being used?
Geostationary
(c) What is the purpose of the curved reflector behind the
aerial? To reflect the signals to a focus at the aerial.
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12. Mirrors are used in many shops and help security guards to
observe customers.
Mirror
Light
(a) Describe what happens to light which strikes the mirror.
It reflects off the mirror at the same angle.
The angle of reflection is equal to the angle of incidence.
(b) Complete the following diagram, showing the incident light
ray and any other ray produced.
Mirror
normal
Incident light ray
reflected light ray
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13. Some lamps use a bundle of optical fibres.
(a) What are optical fibres?
Long, thin strands of flexible glass through which light can
travel.
(b) Describe how optical fibres are used in modern
communication systems.
A signal is changed into variations in brightness of light.
These variations are carried from one end of the fibre to the
other by total internal reflection.
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14. Copper wire is used to transmit electrical signals.
Copper wire
Electric signal
However, copper is expensive, heavy and produces heat energy.
Signals can now be sent through optical fibres and less energy is
wasted.
(a) Describe the type of signal which is transmitted through an
optical fibre.
The signal travels through the fibre as variations in the
brightness of the light.
(b) At what speed does this signal travel through the optical
fibre?
200 000 000 metres per second.
(light travels a little slower in glass than it does in air.)
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14. continued,
(c) Complete the diagram below to show how the signal reaches
the end of the optical fibre.
Out
In
The light repeatedly reflects off the inside walls of the fibre
by total internal reflection until it leaves at the far end.
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15. Dawn is sitting at home using her personal computer. She can use
the computer to gain access to information on the Internet.
Information is transmitted to Dawn's
computer along an optical fibre.
What other device in the home might be
connected to this optical fibre?
The telephone or television.
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16. A television aerial is used to receive signals from the various TV
transmitters.
Some other houses in the street receive their television signals
via optical fibres.
T.V. aerial
Street
Give one advantage and one disadvantage of the use of optical
fibres to transmit signals.
Advantage: don’t need aerials/dishes;
not affected by bad weather
Disadvantage: the street/garden has to be dug up to install it
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17. A telephone message is transmitted from Glasgow to Edinburgh.
(a) What name is given to the part of the system which sends
the signal ?
The transmitter.
(which is the microphone in the mouthpiece)
(b) What name is given to the part of the system which picks up
the signal?
The receiver.
(which is the loudspeaker in the earpiece)
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18. Telephones are of various types and are linked in different ways.
The signal can be transmitted between phones using three
different types of link.
What are the three methods of transmitting a message between
the transmitting and receiving telephones?
- by wires
- by radio signals
- by optical fibres
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19. Mobile phones are being used more and more in the modern
world.
The mobile phone is a small portable telephone which has no
external wiring, unlike conventional phones.
(a) What are the two essential parts of a mobile phone, which
allows the user to send and receive messages?
the mouthpiece (transmitter)
the earpiece (receiver)
(b) Using a mobile phone is not always the best way of contacting
someone.
Give one advantage and one disadvantage of mobile phone use.
advantage: people can get in touch quickly and easily
disadvantage: there is no signal in some areas of the country;
it’s use can distract drivers and cause accidents
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20. While dismantling a telephone in the Physics lab,
Alex discovers a microphone inside the handset.
(a) Was the microphone found inside the
mouthpiece or earpiece?
inside the mouthpiece
(b) A loudspeaker was also removed from the telephone
handset.
Which part of the handset contained the loudspeaker?
the earpiece
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21. Microphones are used in phones, tape recorders and public
address systems.
State the energy change which takes place in a microphone.
sound energy to electrical energy
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22. Loudspeakers are used in phones, stereo systems, radios and
televisions.
State the energy change which takes place in a loudspeaker.
electrical energy to sound energy
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23. A telephone cable contains bundles of copper wire which
carry the signal.
What is the approximate speed of the signal which travels
along the wire?
300 000 000 metres per second (the speed of light)
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24. A book publisher has to send a price list to a school.
The price list is required urgently.
(a) How could the price list be sent to the school very quickly?
You should describe the transmitter, receiver and how the two
are linked together.
It could be sent by fax.
The list is scanned by the sending fax machine.
The image is sent as signal along the phone line.
Another fax machine prints out a copy at the other end.
(b) Why is this method used so often nowadays?
It is much faster than sending a copy of the list by post.
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25. A signal generator is used to produce sounds from a loudspeaker.
The loudness and the frequency of the note can be changed.
The signal is displayed on the screen of an oscilloscope.
Signal
Generator
Oscilloscope
Loudspeaker
(a) Describe how the oscilloscope pattern changes when the
loudness of the sound increases and the frequency stays the
same.
The height of the wave on the screen gets bigger,
but the number of waves does not change.
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25. A signal generator is used to produce sounds from a loudspeaker.
The loudness and the frequency of the note can be changed.
The signal is displayed on the screen of an oscilloscope.
Signal
Generator
Oscilloscope
Loudspeaker
(b) Describe how the oscilloscope pattern changes when the
frequency increases and the loudness stays the same.
The number of waves across the screen changes,
but the height of the waves does not change.
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26. Use the information in the given passage to answer the questions
below.
(a) Complete the following sentences:
radio
Satellites receive ..........................
signals transmitted from
Earth.
radio
transmits
The satellite then ..........................
these ..........................
signals
earth
back to ..........................
(b) Explain the meaning of the term "Geostationary satellite"
A satellite which stays above the same point on the equator.
(c) Why are Geostationary satellites very useful in modern
communication systems?
There is no need to adjust the positions of the ground station
satellite dishes.
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27. The graph below shows how the time it takes a satellite to go
round the Earth changes with its height above the Equator.
(a) Use the graph to find the height of a Geostationary satellite.
The period is 24 hours which is about 38 000 km
(b) A spy satellite has to orbit the Earth twice each day.
Use the graph to find the height of this spy satellite.
A period of 12 hours is at a height of 21 000 km
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28. The telecommunication system linking two towns uses copper
wires. This system is being replaced by one which uses optical
fibres. Jamil and Gina want to compare the time taken for
signals to travel through these two different types of
connector, copper wires and optical fibres.
A length of copper wire and a length of optical fibre are each
connected to a telephone and a timing device as shown in the
diagram.
Copper Wires
Timing
Device
Gina
Optical fibre
Timing
Device
Jamil
The timing device can measure the time it takes a signal to
travel along the copper wire and the optical fibre.
(a) Give two reasons why this not a fair test.
The wires and fibres are different lengths – this would make a difference
They are different thicknesses – this would not make a difference
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28. (b) Jamil and Gina changed their test to make it fair.
The time taken for the signal to travel each of the connectors is
given in the table below.
Type of Signal
Electrical
Time(seconds)
0.00015
Light
0.0002
(i) Which signals, electrical or light, take the shortest time to
travel along the connector?
The electrical signals take the shorter time to travel.
(ii) Explain in which connector, copper wire or optical fibre, the
signals take least time to travel.
The signals take less time in the copper wire.
This is because the electrical signal travels faster in the wires
than the optical signal in the fibre.
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29. A student finds the following table in a physics book.
It contains information on groups of radio waves.
Frequency Name
Frequency range
Main Use
Ultra High Frequency 300 MHz to 3 000 MHz
TV and mobile phones
Medium Wave
300 kHz to 3 MHz
Radio communication
Short Wave
3 MHz to 300 MHz
High quality radio communication
Long Wave
30 kHz to 300 kHz
Long range radio communication
Complete the following diagram which shows the radio frequency
ranges and their uses.
Use the information in the table above to complete your diagram.
The use of 300 kHz to 3 MHz has been filled in for you.
Use of frequency Range
long range
radio
communication
30 kHz
Radio
Communication
300 kHz
high quality
TV and mobile
radio
phones
communication
3 MHz
Frequency
300 MHz
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3 000 MHz
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30. The following is part of a crossword puzzle that has clues about
telecommunications.
1a
Complete the part of the crossword shown.
2g
m
The clues are as follows:
3s p e e d
DOWN:
o
l
1. This part of the radio needs a battery
s
i
to supply it with energy.
t
f
2. Twenty four hour per day communication
a
i
systems often use this type of satellite. 4
t
w h i t e
ACROSS:
i
r
3. Radio signals travel from Glasgow to
o
London in a very short time. This is
n
because radio waves have a very high
a
4. Mixing red, green and blue light
r
produces this colour.
y
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Intermediate 1
Physics
Telecommunication
End of
Questions and
Answers
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