Beath High School - Int 1 Physics1 Intermediate 1 Physics Telecommunication Questions and Answers.
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Transcript of Beath High School - Int 1 Physics1 Intermediate 1 Physics Telecommunication Questions and Answers.
Beath High School - Int 1 Physics 1
Intermediate 1 Physics Telecommunication Questions
andAnswers
Beath High School - Int 1 Physics 2
Intermediate 1 Physics TelecommunicationQuestions 1 to
10Questions 11 to 20Questions 21 to 30
Beath High School - Int 1 Physics 3
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.
Beath High School - Int 1 Physics 4
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.
(b) At what speed does the signal travel?
(c) What is transferred from the radio mast to the
aerial in her radio?
The transmitter sends out invisible waves of energywhich we call radio waves.
energy
Three hundred million metres per second (300 000 000 m/s)
Beath High School - Int 1 Physics 5
3. Raymond has drawn a block diagram for a radio but can only remember the first unit.
(a) Complete the correct block diagram for the radio system.
(b) Describe the function of any three units within the radio receiver. Aerial - Detects all radio waves.Tuner - Selects one radio station.Decoder - Separates the sound signal from the radio waveAmplifier - Makes the small electrical signal stronger.Power Supply - Supplies extra energy to the amplifier.Loudspeaker - Changes the electrical signal into sound.
aerial tuner decoder amplifier
speaker
Power
supply
Beath High School - Int 1 Physics 6
4. A radio display shows a combination of letters and
numbers as shown.
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 ofwaves produced every second.)
FM 102.5 MHz
Beath High School - Int 1 Physics 7
5. Jason is checking the times of the football broadcasts in his newspaper.
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.
Radio Station Time Programme
Radio Clyde 2 2.00 p.m. “Sportsound”
Westsound 2.00 p.m. “Sportsound”
Beath High School - Int 1 Physics 8
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?
(b) What is the difference between the two
waves?
Radio waves.
They are different frequencies.
Beath High School - Int 1 Physics 9
7. Each television station has a name which we are
all familiar with.
BBC 1; BBC 2; STV;
Channel 4; Channel 5
As well as the name, how can a particular
broadcast station be identified?
It can be identified by its frequency.
Beath High School - Int 1 Physics 10
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
speaker
Visiondecoder
Picturetube
Visionamplifier
sounddecoder
soundamplifier
Beath High School - Int 1 Physics 11
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
tuner
speaker
Visiondecoder
Picturetube
Visionamplifier
sounddecoder
soundamplifier
- The decoders separate the sound and vision signals from the carrier wave.
- The tuner selects the signal you want.(i.e. the channel of your choice)
- The aerial detects many radio signals and changes them into electrical signals.
- The amplifiers make the electricalsignals stronger.
- The loudspeaker changes the audio signal into a sound wave,
- The picture tube changes the video signal into pictures.
Beath High School - Int 1 Physics 12
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.
Beath High School - Int 1 Physics 13
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.
(b) Weather forecasters on television show us detailed pictures of rain clouds over Britain.
How is this kind of information gathered?
It is transmitted up to a satellite in orbit.
A satellite in orbit around the earth takes pictures
and transmits them back to earth.
There it is amplified and then retransmitted to Cornwall.
Beath High School - Int 1 Physics 14
11. An army unit on military exercise at the Earth's equator have positioned a satellite dish as shown.
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?
(b) What name is given to the type of satellite being used?
(c) What is the purpose of the curved reflector behind the aerial?
The satellite stays at the same point above the equator.
Geostationary
Aerial
DishAerial
Curved refl ector
To reflect the signals to a focus at the
aerial.
Beath High School - Int 1 Physics 15
I ncident light ray
Mirror
12. Mirrors are used in many shops and help security guards to observe customers.
(a) Describe what happens to light which strikes the mirror.
(b) Complete the following diagram, showing the incident light ray and any other ray produced.
It reflects off the mirror at the same angle.The angle of reflection is equal to the angle of incidence.
normal
Mirror
Light
reflected light ray
Beath High School - Int 1 Physics 16
13. Some lamps use a bundle of optical fibres.(a) What are optical fibres?
(b) Describe how optical fibres are used in modern communication systems.
Long, thin strands of flexible glass through which light cantravel.
A signal is changed into variations in brightness of light.These variations are carried from one end of the fibre to
theother by total internal reflection.
Beath High School - Int 1 Physics 17
14. Copper wire is used to transmit electrical signals.
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.
(b) At what speed does this signal travel through the optical fibre?
The signal travels through the fibre as variations in thebrightness of the light.
Electric signal
Copper wire
200 000 000 metres per second. (light travels a little slower in glass than it does in air.)
Beath High School - Int 1 Physics 18
I n
Out
14. continued, (c) Complete the diagram below to show how the signal reaches the end of the optical fibre.
The light repeatedly reflects off the inside walls of the fibreby total internal reflection until it leaves at the far end.
Beath High School - Int 1 Physics 19
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'scomputer along an optical fibre.
What other device in the home might beconnected to this optical fibre?The telephone or television.
Beath High School - Int 1 Physics 20
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.
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
Street
T.V. aerial
Disadvantage: the street/garden has to be dug up to install it
Beath High School - Int 1 Physics 21
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 ?
(b) What name is given to the part of the system which picks up the signal?
The transmitter.
The receiver.
(which is the microphone in the mouthpiece)
(which is the loudspeaker in the earpiece)
Beath High School - Int 1 Physics 22
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
Beath High School - Int 1 Physics 23
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?
(b) Using a mobile phone is not always the best way of contactingsomeone.Give one advantage and one disadvantage of mobile phone use.
the mouthpiece (transmitter)
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
the earpiece (receiver)
Beath High School - Int 1 Physics 24
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?
(b) A loudspeaker was also removed from the telephone handset.Which part of the handset contained the
loudspeaker?
inside the mouthpiece
the earpiece
Beath High School - Int 1 Physics 25
21. Microphones are used in phones, tape recorders and publicaddress systems.State the energy change which takes place in a microphone.
sound energy to electrical energy
Beath High School - Int 1 Physics 26
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
Beath High School - Int 1 Physics 27
23. A telephone cable contains bundles of copper wire whichcarry 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)
Beath High School - Int 1 Physics 28
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.
(b) Why is this method used so often nowadays?
It could be sent by fax.
It is much faster than sending a copy of the list by post.
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.
Beath High School - Int 1 Physics 29
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.
(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.
SignalGenerator
Oscilloscope
Loudspeaker
Beath High School - Int 1 Physics 30
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.
(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.
SignalGenerator
Oscilloscope
Loudspeaker
Beath High School - Int 1 Physics 31
radio
radiotransmits
earth
26. Use the information in the given passage to answer the questions below.
(a) Complete the following sentences:
Satellites receive .......................... signals transmitted
from Earth.
The satellite then .......................... these ..........................
signals back to .......................... (b) Explain the meaning of the term "Geostationary satellite"
(c) Why are Geostationary satellites very useful in modern communication systems?
A satellite which stays above the same point on the equator.
There is no need to adjust the positions of the ground station
satellite dishes.
Beath High School - Int 1 Physics 32
Time to go round
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.
(b) A spy satellite has to orbit the Earth twice each day.Use the graph to find the height of this spy satellite.
The period is 24 hours which is about 38 000 km
A period of 12 hours is at a height of 21 000 km
Beath High School - Int 1 Physics 33
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.
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
differenceThey are different thicknesses – this would not make a difference
TimingDevice
TimingDevice
Copper Wires
Optical fi bre
Gina
J amil
Beath High School - Int 1 Physics 34
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.
(i) Which signals, electrical or light, take the shortest time to travel along the connector?
(ii) Explain in which connector, copper wire or optical fibre, the signals take least time to travel.
The electrical signals take the shorter time to travel.
The signals take less time in the copper wire.
Type of Signal Time(seconds)
Electrical 0.00015
Light 0.0002
This is because the electrical signal travels faster in the wires
than the optical signal in the fibre.
Beath High School - Int 1 Physics 35
RadioCommunication
Use of f requency Range
Frequency
30 kHz 300 kHz 3 MHz 300 MHz 3 000 MHz
29. A student finds the following table in a physics book.It contains information on groups of radio waves.
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.
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
long rangeradiocommunicatio
n
high qualityradiocommunicatio
n
TV and mobile phones
Beath High School - Int 1 Physics 36
12
3
4
30. The following is part of a crossword puzzle that has clues about telecommunications.Complete the part of the crossword shown.The clues are as follows:DOWN:
1. This part of the radio needs a batteryto supply it with energy.
2. Twenty four hour per day communicationsystems often use this type of satellite.
ACROSS:3. Radio signals travel from Glasgow to
London in a very short time. This isbecause radio waves have a very high
4. Mixing red, green and blue lightproduces this colour.
amplifier
geostationary
s e d
w h i t
Beath High School - Int 1 Physics 37
Intermediate 1 Physics Telecommunication End ofQuestions and
Answers