Transcript General

Intermediate 1
Physics
Telecommunication

Radio

Television

Satellites

Optical Fibres

Telephone
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Intermediate 1
Physics
Telecommunication

Radio
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Radio
At one time a radio was called a "wireless"
because the signal it received did not come
through wires.
w____.
A radio transmitter ssends
_ _ _ _ out invisible
waves of energy which can be picked up by
an aerial rreceiver.
_______.
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Radio

The radio waves can travel through air
the air at a speed of 300 000 000
metres per ssecond.
_____.
(300 000 000 = 300 hundred million.)
This means that they travel large
l____
distances in a very short time.
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Radio
Parts of a radio receiver

A radio is an electronic system which
is used to detect radio waves
w _ _ _ _
and change them into speech and
music.

Every radio has five main parts, all
having a different jjob
_ _ to do.
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Radio
Parts of a radio receiver
The five parts are,
aaerial
_____
t____
tuner
d______
decoder
a________
amplifier
l_________
loudspeaker
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Functions of the main parts of a radio
Aerial
- Detects all r _radio
_ _ _ waves.
Tuner
- Selects one radio s _ station
_ _ _ _ _ by picking
out one frequency.
sound
Decoder
- Separates the s _
_ _ _ signal from the
radio wwave.
_ _ _.
Amplifier
- Makes the small electrical ssignal
_____
stronger. (The extra e _energy
_ _ _ _ is supplied
to the amplifier by a battery or the mains).
Loudspeaker - Changes the e _ _electrical
_ _ _ _ _ _ _ signal into
a sound wave.
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Radio frequency
Each radio station broadcasts on a
d _ _different
_ _ _ _ _ _ radio frequency.
The f _ _ frequency
_ _ _ _ _ _ of a wave is the
number of waves produced in one second.
The frequency is measured in h _hertz
_ _ _ (Hz).
1 000 Hz = 1 _ _ _kilo
_ hertz (kHz)
This means 1 000 waves in one second.
1 000 000 Hz = 1 _ _ mega
_ _ hertz (MHz)
This means 1 000 000 waves in one second.
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Radio frequency
A h high
_ _ _ frequency wave looks like this:
A l low
_ _ frequency wave looks like this:
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Radio frequency
You can ttune
_ _ _ a radio by selecting
the frequency you want.
Radio Tuner Panel
MW
kHz
600
1000
1400
FM
MHz
90
100
105
Forth 1 has a frequency of
Frequency selected
_ 97.3
_ . _ MHz
( 97 300 000 Hz) and is a local FM radio
station.
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Radio frequency
The medium wave band (MW) contains lower
l _ _ _ _
frequency radio stations like Radio 5, which has a
frequency of 909 kHz ( _ _909
_ 000
_ _ _ Hz).
Signs at the side of motorways give d
_ _ _ _ _ _
drivers
information about radio frequencies.
Radio 1
99.5 FM
Radio Scotland
810 MW
Frequency = 99.5 MHz (= 99 500 000 Hz)
Frequency = 810 kHz (= 810 000 Hz)
FM stations have a
higher frequency than
medium wave (MW).
FM stations have a
h _higher
_ _ _ _ frequency than
medium wave (MW)
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Intermediate 1
Physics
Telecommunication

Television
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Television
A television receiver picks up very high
h _ _ _
frequency radio waves.
These signals travel at 300 million m
_ _ _ _ _
metres
per second through the air but have a higher
frequency than signals from a radio
r _ _ _ _
transmitter.
This means radio and T.V. signals travel
at the s _same
_ _
speed
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Television
television
speed =
_ _ _ 300
_ _ 000
_ _ 000
_ _ m/s
uses very hhigh
_ _frequency
_ f _ _ _ _ _ _ _ _
waves
radio
speed =
_ _ _ 300
_ _ 000
_ _000
_ _ m/s
uses lower frequency wwaves
_ _ _
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Television
Each television station transmits a
d _ _ _ _ _ different
_ _ _ frequency.
The following table shows some of the well known
television stations and frequencies they use in one
area of Scotland.
Station
Frequency
BBC 1
623 MHz
BBC 2
671 MHz
Channel 4
703 MHz
Channel 5
599 MHz
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Parts of a television receiver
Aerial
tuner
Sound
decoder
Vision
decoder
Sound
amplifier
Vision
amplifier
loudspeaker
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Picture
tube
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Parts of a television receiver
- The aerial detects many r _radio
_ _ _ signals
Aerial
and changes them into eelectrical
________
signals.
tuner
- The t tuner
_ _ _ _ selects the signal you want.
(i.e. the chchannel
_ _ _ _ _ of your choice)
Sound
decoder
Vision
decoder
- The decoders separate the sound and
vision signals from the ccarrier
______
wave.
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Parts of a television receiver
- The amplifiers make the electrical
Sound
amplifier
Vision
amplifier
s___
_ _ _ stronger. One amplifier is
signals
for the s _
_ _ _ signal and the other
sound
amplifier is for the p _picture
_ _ _ _ _ signal.
- The l _ _loudspeaker
_ _ _ _ _ _ _ _ changes the
loudspeaker
Picture
tube
audio signal into a sound wave,
- The p _ _picture
_ _ _ _tube
t _ _ _ changes the
video signal into pictures.
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Television – Colour pictures
In a colour television only three
t _ _ _ _
colours can be produced on the screen.
The three colours are R Red,
_ _ , Green
G _ _ _ _
and
B _ _ _ .
Blue.
All the other colours are produced by
m _ _mixing
_ _ _
these three colours.
When RED, GREEN and BLUE are all mixed
together
W WHITE
_ _ _ _
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is produced.
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Television – Colour pictures
Any colour can be made by mixing the l _ _
_ _
light
of
these colours.
You can remember the order of colours in the "star" by
remembering the following:
Rich Young
RRed
__
YYellow
_____
Girls
G
____
Green
Can
Buy
Meals
C___
Cyan
B___
Blue
M______
Magenta
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Television – Colour pictures
RED + GREEN = YYELLOW
_____
GREEN + BLUE = C
____
CYAN
BLUE + RED = M
______
MAGENTA
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Intermediate 1
Physics
Telecommunication

Satellites
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Satellites
Radio waves can be sent around the
w world
_ _ _ _ via satellites.
For example, the American Superbowl
competition can be seen l _live
_ _ in the
U.K. because of the signal being passed
on by ssatellite.
_ _ _ _ _ _ _ _.
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Uses of satellites
Modern satellites can beam various signals back to the
ground. For example:
T.V. programmes
p _ _ _ _ _ _ _ _ _
p _ phone
_ _ _
calls
w _ _weather
_ _ _ _
t _ _ tracking
_ _ _ _ _
pictures
stolen cars.
The satellites o _ orbit
_ _ _ the earth and
t _ _ transmit
_ _ _ _ _
signals to or
r _ receive
_ _ _ _ _ signals from ground
stations.
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Geostationary satellites
Satellite
above the
Equator
Receiver in
Cornwall
Equator
Transmitter in
South Africa
A Geostationary satellite always remains above the same
s ___
point of the Equator on the Earth's surface.
The dish on the ground can be set to receive a strong
signal and not be
m _moved
_ _ _
again.
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Geostationary satellites
Geostationary Satellites Orbits once every _24
_ hours
Orbits above the EEquator.
______.
Other Satellites
Several orbits completed every
24 hours. Height is l _
_ _ than
less
that of Geostationary
satellites.
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Curved Reflectors
The signals from satellites travel great distances and a
bare aerial cannot pick up a
s _ _ _
_ _ enough
e _ _ _ _ _
strong
signal.
A curved reflector can bring radio waves to a ffocus
____
just like curved mirrors cause l _ light
_ _ _ rays to
meet at the focus.
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Curved Reflectors
Ray diagram showing how radio waves are
brought to a f _focus
_ _ _ by a
ccurved
_ _ _
_ _ r _ _ _ _ _ _ _ _.
reflector.
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Curved Reflectors
Aerial placed
at the ffocus
____
C_____
Curved
reflector receiver
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Curved Reflectors
A strong/weak radio signal can be detected if the aerial is
positioned at the focus of the curved reflector.
More/Less of the wave energy is collected when these
aerials are used.
(This is because the dish collects more/less of the energy
in the wave than a bare aerial.
Also its curved shape
f _ _ _ _ _ _
focuses
the collected
energy on to the aerial.)
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Curved Reflectors
Very large dish aerials are used to
detect radio waves from distant stars.
These detectors are called radio
r _ _ _ _
ttelescopes.
_ _ _ _ _ _ _ _ _ .
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Intermediate 1
Physics
Telecommunication

Optical fibres
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Reflection
We can look at our
Plane Mirror
rreflection
_________
i
in a mirror or the light from any
shiny object being reflected.
i = angle of incidence normal
The angles i and r are the ssame
_ _ _ size.
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r
the angle of
reflection
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Optical fibres
At one time signals always were sent through copper w
____.
wires.
An e _ _ electrical
_ _ _ _ _ _ _ current flows through
the phone lines but e _
_ _ _ _ is lost and the signal needs
energy
to be boosted every so often at repeater stations. An
optical fibre is a very
which can carry
t thin
_ _ _ piece of flexible glass
g____
l _light
_ _ _ energy. The light is
r__
_ _ _ _ _ _ between the sides of
reflected
the optical fibre.
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Optical fibres
In air, light travels at the
s _same
_ _
speed as radio waves,
_ _300
_ million metres per second.
In optical fibres, the light travels slightly
s _slower
_ _ _ _ at
200 million metres per second.
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Uses of optical fibres
More and more people are receiving signals into their homes
which have come through optical fibres,
f _ _ _ _ _ ,
for example:
cable ttelevision
_ _ _ _ _ _ _ _ _
p _phone
_ _ _ calls
h home
_ _ _ banking
I _ _Internet
_ _ _ _ _ access
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Uses of optical fibres
One disadvantage of using optical fibres is the inconvenience
of having to lay the cables underground
u _ _ _ _ _ _ _ _ _ _
which means digging trenches along the pavements.
One advantage is not having to install a satellite dish
d _ _ _
on the wall of the house. Another advantage is that the
reception is not affected by
conditions, e.g. heavy
b bad
_ _
weather
s _ _ _ .
snow.
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Optical fibres
Comparison of Copper cable and Optical Fibre:
Copper Cable
Optical Fibre
Repeater stations every 4 km
Repeater stations every 1100
_ _ km
1 000 conversations at a time
11 000
000 conversations at a time
11
Thick and heavy
TThin
_ _ _ and very llight
____
Almost 300 million metres per second
_200
_ _ million metres per second
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Intermediate 1
Physics
Telecommunication

Telephone
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Telephone
People can speak to each other, over
l _ _ _
long
distances, by telephone.
Speech is changed into an electrical
e _ _ _ _ _ _ _ _ _
signal and changed back into s _sound
_ _ _
again at
the receiver.
Sound
Mouthpiece
microphone
m………….
Link:copper wire
Carrier: electrical signal
Transmitter
T…………..
Earpiece
Sound
l..………….
loudspeaker
Receiver
R………….
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Telephone
Part
Energy Change
microphone
Sound to electrical
loudspeaker
Electrical to sound
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Telephone
Phones can be connected by copper
w wire
_ _ _ or
optical f _fibre
_ _ _ (shown below).
Mouthpiece
M………….
Sound
microphone
Link:o…….
optical f…….
fibre
Link:
Carrier:
signal
Carrier: l…….
light signal
Earpiece
E………….
loudspeaker
Transmitter
Sound
Receiver
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Mobile phones
Mobile phones rely on
r _radio
_ _ _ signals
travelling from the transmitter to the
r _ _receiver.
_ _ _ _ _ . These signals carry
the message through air without wires.
Sound
Mouthpiece
microphone
Link: no physical link
Carrier: radio
r…….wave
w…..
Carrier:
Earpiece
loudspeaker Sound
Transmitter
Receiver
A mobile phone has to be a combined radio
t _ _transmitter
_ _ _ _ _ _ _ _ and receiver.
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Mobile phones
There are advantages and disadvantages to
using a mobile phone.
You do not have to find a phone box when you
want to make an urgent call. However, some
drivers cause accidents
a _ _ _ _ _ _ _ _
when they use a
m _ mobile
_ _ _ _
phone
and drive at the same time.
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Mobile phones
Some locations prevent you using the mobile
phone, for example:
• in the Scottish
H _ _ _ _ _ _ _ _
Highlands
(the hills s _
_ _ the signal)
stop
• inside
l _long
_ _
tunnels.
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Energy changes in a telephone system
Mouthpiece
A mouthpiece transmits the message. S _Sound
_ _ _ energy
enters the m _ _ mouthpiece
_ _ _ _ _ _ _
into electrical
and is changed
e _energy
_ _ _ _ .
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Energy changes in a telephone system
Earpiece
An earpiece receives the message.
Electrical energy is changed back to
s _sound
_ _ _
in the
loudspeaker.
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Energy changes in a telephone system
Telephone signals
Copper wires carry the message in the form of an
e _ _ _ _electric
_ _ _ current
c _ _ _ _ _ _ ,
which travels at almost _ 300
_ _ million metres per second.
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Fax
Fax is the shortened term for facsimile.
f _ _ _ _ _ _ _ _ .
A document is inserted into the machine and a
c _ _ _
copy
of the document is received at the other
end of the p _phone
_ _ _
line.
Important documents can be transferred very qquickly.
_ _ _ _ _ _.
Before this invention, documents had to go by ppost.
_ _ _ .
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Oscilloscope patterns
The signal in a phone line can be displayed on the screen of
an oscilloscope. The
v _ _
_ _ _ _
voltage
of the signal
varies as the caller speaks into the mouthpiece.
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Oscilloscope patterns
Loudness
Loud sounds produce a
h _ higher
_ _ _ _
than a quiet soft sound. The
voltage signal
a _ _ amplitude
_ _ _ _ _ _
is
greater for high voltages.
Loud note
has large
amplitude
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Quiet note
has s............
smaller
amplitude
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Oscilloscope patterns
Frequency
Some sounds have a higher pitch (frequency) than others.
For example, sound ‘A’ below could be a horn which produces
a
l low
_ _
pitched sound. Sound ‘B’ below could be a
whistle which produces a high pitched
p _ _ _ _sound.
__s _ _ _ _ .
Sound A
has a low
frequency
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Sound B
has a h........
high
f..................
frequency
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Oscilloscope patterns
The oscilloscope can display waves of different frequencies.
A high frequency wave produces
m more
_ _ _
waves per
second than low a frequency wave.
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Intermediate 1
Physics
Telecommunication
End of Unit
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