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


Intermediate 1 Physics TelecommunicationQuestions 1 to

10Questions 11 to 20Questions 21 to 30


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.


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)


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


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


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”


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.


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.


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


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.


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.


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.


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.


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


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.


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.)


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.


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.


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


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)


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


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)


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


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


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


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)


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.


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


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


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.


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


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


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.


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


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


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Beath High School - Int 1 Physics1 Intermediate 1 Physics Telecommunication Questions and Answers.

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