Name: Class:

Duncanrig Secondary SchoolEast Kilbride

S3 Physics Elective

Telecommunications

Pupil Booklet Learning Outcomes Homework Summary

SCN 3-11bBy exploring radiations beyond the visible, I can describe a selected application, discussing the advantages and limitations.

SCN 4-11bBy carrying out a comparison of the properties of parts of the electromagnetic spectrum beyond the visible, I can explain the use of radiation and discuss how this has impacted upon society and our quality of life.

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Content Statements Can you do this?

Comments

Radio1 State that the main parts of a radio receiver are: Aerial, tuner, decoder, amplifier, loudspeaker, electricity supply; and identify these parts on a block diagram.

2 Describe in a radio receiver the function of: Aerial, tuner, decoders, amplifier, loudspeaker, electricity supply.

3 Describe the general principle of radio transmission in terms of transmitter, carrier wave, amplitude modulation, receiver.

4 Identify from drawings the various wave forms associated with radio

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transmission.Analogue and Digital Radio

1 Be able to identify analogue and digital signals from wave forms.

2 Calculate the binary equivalent of a decimal number in the range 0 to 12.

3 State some of the advantages that digital radio has over analogue radio.

Television1 State that television transmission is similar in principle to radio transmission.

2 Describe how a moving picture is seen on a television screen in terms of: image retention.

3 State that mixing red, green and blue lights produces all colours seen on a colour television screen.

4 Describe the effect of colour mixing lights (red, green and blue).

5 Compare the properties of different types of modern television.

Diffraction and Reflection1 State that diffraction is the bending of waves passing through a gap or round the edge of an obstacle.

2 Explain in terms of diffraction how wavelength affects radio and television reception.

3 State that light can be reflected

4 Describe the direction of the reflected light ray from a plane “mirror”.

5 State what is meant by an optical fibre.

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6 State that electrical cables and optical fibres are used in some telecommunication systems.

7 Describe one practical example of telecommunication which uses optical fibres.

8 State that signals travel along optical fibres at very high speed

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Curved Reflectors and Satellites1 State that curved reflectors on certain aerials or receivers make the received signal stronger.

2 Explain why curved reflectors on certain aerials or receivers make the signal stronger.

3 Give examples of where curved reflectors are used.

4 State that the period of satellite orbit depends on its height above the Earth.

5 State that a geostationary satellite stays above the same point on the Earth’s surface.

6 Describe the principle of transmission and reception of satellite television broadcasting using geostationary satellites and dish aerials.

7 Describe the principle of intercontinental telecommunication using a geostationary satellite and ground stations.

Modern Communication Methods1 State that the internet is the underlying telecommunications network that makes the world wide web possible.

2 Name applications that use the internet.

3 State that the internet uses a mixture of electrical cables, optical fibres, radio waves and satellite links to send information.

4 State that the telephone is an

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example of long range communication between transmitter and receiver.

5 State the energy changes a) In a microphone (sound electrical) b) In a loud speaker (electrical sound).

6 State that the mouthpiece of a telephone (transmitter) contains a microphone and the earpiece (receiver) contains an earphone (loudspeaker).

7 State that an electrical signal is transmitted along a wire at a speed much greater than the speed of sound (almost 300 000 000 m/s).

8 State that mobile phones use microwaves to transmit information.

9 State thata) mobile phone networks use

“cells” and at the centre of each cell is a base station

b) the base station sends and receives calls from your phone.

10 Make a reasoned argument whether mobile phones are a danger to health or not.

Wave Properties1 State that waves are one way of transmitting signals.

2 Use the following terms correctly in context: wave, frequency, wavelength, speed, energy (transfer), amplitude.

3 Describe, with examples, how the following terms relate to sound: frequency and amplitude.

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4 Carry out calculations involving the relationship between distance, time and speed in problems on sound, light, radio, TV and microwaves.

5 Carry out calculations involving the relationship between speed, wavelength and frequency for sound, light, microwaves, television and radio waves.

6 Note the equivalence of f and d/t.

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Elective Homework – Getting Started

Success involves doing many kinds of problems which help improve your knowledge and understanding of the ideas in the course and your ability to solve problems. To get started we will look at a general method for tackling problems.

General Method for Solving Problems.

Any numerical problem in Physics can be solved using the following steps:

Read the question carefully. Find out exactly what is being asked. Extract the key data. Select the correct equation. Substitute the data into the equation and find the missing variable. Give the answer and correct unit.

ExampleHow far does a cyclist travel in 26 seconds if she is travelling at a constant speed of 8 metres per second?

Solution

Read the question carefully

Find out exactly what is being asked Distance (how far)

Extract the key data time = 26 secondsspeed = 8 metres per second

Select the correct equation distance = speed x timeSubstitute data into equation d = 8 x 26Give the answer and correct unit d = 208 m

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Usual Layout

d = ?v = 8 m/st = 26 s

d = v x t = 8 x 26 = 208 m

All numerical questions in the following homework exercises should be carried out in this way. No marks will be awarded for an answer given without the working being shown.

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Helpful Hint

Always watch the units in an equation. They may need to be converted before being put into an equation.

e.g. 3 mA = 0.003 A = 3 x 10-3 A6 km = 6000 m = 6 x 103 m

Homework Exercise 1 – Radio, Analogue and Digital.You will find help with this exercise on pages 22 and 23.

1. (a) Copy the table below and fill in the correct definition for each item.

(6)

PART FUNCTIONAerialTunerDecoderAmplifierLoudspeakerElectricity supply

(b) Draw a block diagram to show how the parts of a radio receiver are connected together.

(3)

2. (a) Explain what is meant by an amplitude modulated wave. (2)(b) Draw an amplitude modulated wave.

(1)(c) The radio frequency of the modulated wave is called the carrier wave. Why do you think it gets this name?

(1)

3. Which of the following is an analogue signal and which is digital?

(1)

Signal A Signal B

4. Convert the decimal number 7 into binary.(1)

Total (15)

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Homework Exercise 1 – Radio, Analogue and Digital.Put your answers here

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red

blue green

Homework Exercise 2 – Television.You will find help with this exercise on pages 23 and 24.

1. (a) Explain what is meant by persistence of vision.(1)

(b) How does persistence of vision help create a moving picture?

(1)

2. A colour television produces millions of colours on the screen.

(a) Name the colours that are used to produce all the colours seen on a TV screen.

(1)(b) How are these colours used to produce the millions of colours seen on a TV screen?

(1)

3. Copy and complete the diagram below to show how red, blue and green light mix. You do not need to use colour, labels will do.

(2)

Total(6)

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Homework Exercise 2 – Television.Put your answers here.

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Homework Exercise 3 - Diffraction and Reflection.You will find help with this exercise on pages 24 and 25.

1. What word describes the bending of waves around the edge of a barrier?

(1)2. Copy and complete the diagrams below showing what

happens to the waves as they pass round the edge of the barrier. (2)

long wavelengths short wavelengths

3. Copy and complete the diagram below showing the path of the ray of light. Indicate any important information required about the angles in the diagram.

(2)

4. (a) What is an optical fibre?(1)

PTO(b) Copy and complete the diagram to show the path taken by the ray of light passing through an optical fibre.

(1)

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Homework Exercise 3 - Diffraction and Reflection.You will find help with this exercise on pages 24 and 25.

5. (a) Name a communication system that uses optical fibres to transmit information.

(1)(b) In what form is information passed along an optical fibre?

(1)

6. An optical fibre is used to carry a telephone message from the USA to Scotland. It travels 5000km. The light signal travels at a speed of 2 x 108 m/s. How long will this take?

(2)

Total (11)

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Helpful Hint

1 km = 1000 m = 1 x 103 m

Homework Exercise 3 - Diffraction and Reflection.Put your answers here.

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Homework Exercise 4 – Curved Reflectors and Satellites.You will find help with this exercise on pages 26 and 27.

1. Aerials picking up signals from a long distance away often have curved reflectors attached to them.

(a) What is the purpose of the curved reflector?(1)

(b) By use of a diagram show how it does this. (1)

2. The period of a geostationary satellite is 24 hours.(a)Explain what is meant by a geostationary satellite.

(1)(b)What is meant by the word period?

(1)(c)How is a satellite’s period affected by it’s height above

the Earth?(1)

3. Copy the diagram below to show how a curved reflector helps transmit a parallel beam of waves.

(2)

Total(7)

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Homework Exercise 4 – Curved Reflectors and Satellites.Put your answers here.

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Homework Exercise 5 – Modern Communication Methods.You will find help with this exercise on page 27.

1. What name do we give to all the world’s linked up computers?

(1)

2. Name four different ways in which links are made between these computers.

(2)3. What is the job of a router?

(1)4. Copy the diagram of a telephone handset and label the

parts given below.

transmitter, receiver, loudspeaker, microphone(2)

5. What are the main energy changes in:(a) The loudspeaker?

(1)(b) The microphone?

(1)6. Which member of the electromagnetic spectrum is used to

send information across the mobile phone network?(1)

Total (9)

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Homework Exercise 5 – Modern Communication Methods.Put your answers here.

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12 m

2 m

Homework Exercise 6 – Wave Properties 1.You will find help with this exercise on pages 28 and 29.

1. Copy and complete the table below.(6)

WAVE TERM SYMBOL UNIT DEFINITIONfrequencywavelengthspeed

2. The following questions refer to the diagram below:

(a) Calculate the wavelength of the waves shown.(1)

(b) If these waves were produced in 6 seconds, what is their frequency?

(1)(c) What is the amplitude of these waves?

(1)(d) Use the wave equation to calculate the speed of

these waves.(2)

3. Look at this diagram of a sound signal displayed on an oscilloscope. Describe what would happen to its frequency and amplitude in each of the following cases.

(a)The volume of the sound is increased. (1)(b)The pitch is increased and he volume stays the same. (1)(c)The pitch and the volume are decreased. (1)

Total (14)

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Homework Exercise 6 – Wave Properties 1.Put your answers here.

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Homework Exercise 7 – Wave Properties 2.You will find help with this exercise on pages 28 and 29.

1. Find the missing variable in each row of the table. You must show all your working for each missing variable.

(4)

SPEED DISTANCE TIME10 m/s 100 m

3000 m 150 s1.2 m/s 30 s

2. A person at the mouth of a cave shouts, and hears an echo from the back wall of the cave. Using a stopwatch, she times 1 second between shouting and hearing the echo. Calculate how far away the back wall of the cave is. Take the speed of sound to be 340 m/s.

(3)

3.A wave of frequency 8 Hz has a wavespeed of 16 m/s.What is its wavelength?

(2)

4. A wave generator at a swimming pool creates waves which have a wavelength of 2m. If the speed of the waves is 1.2m/s what is their frequency?

(2)

5. The navy use long wavelength radio waves for telecommunications.

Calculate the frequency of a radio wave with a wavelength of 8.6 km used by the navy to communicate at sea. (2)

Total (13)

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Helpful HintsRadio and television waves are electromagnetic waves which travel at a speed of 3 x 108 m/s (300 000 000 m/s).

1 km = 1000 m = 1 x 103 m.

Homework Exercise 7 – Wave Properties 2.Put your answers here.

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Telecommunications - Summary.

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Radio ReceiverThe main parts of a radio receiver can be represented in a block diagram:

The aerial picks up radio waves of many different frequencies and converts them into electrical signals.The tuner selects one particular frequency from the many received by the aerial.The decoder extracts the audio (sound) signal from the transmitted radio signal.The amplifier increases the strength of the electrical signal.The loudspeaker converts the electrical signal into sound.The power supply supplies extra energy for the amplifier.Radio TransmissionRadio signals are produced by changing (modulating) the amplitude of a high frequency carrier wave according to the audio signal that is to be carried. This is known as amplitude modulation (AM).

+ =audio wave carrier wave amplitude modulated waveThese modulated signals are converted from electrical signals into radio waves at the transmitter. The radio waves travel through the air and are converted back to electrical signals at the radio receiver where the audio signal is separated from the radio signal.

In frequency modulation (FM) it is the frequency of the carrier wave that is changed by the audio signal. FM gives better quality sound as is less likely to be affected by interference.

frequency modulated wave

Power supply

aerial tuner decoder amplifier loudspeaker

Telecommunications - Summary.

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Digital Radio

A digital signal is just a sequence of ones and zeros. It must be decoded in some way before it can be understood.

Analogue Signal Digital Signal

Binary numbers are a way of converting decimal numbers into ones and zeros.

decimal 1 2 3 4 5 6 7 8 9binary 0001 0010 0011 0100 0101 0110 0111 1000 1001

Television

The parts of a television are similar to that of the parts of a radio receiver.

A moving picture is produced because there are many different pictures produced each second. 25 pictures are produced each second and because our eyes retain the previous picture on the retina for a short time we do not see the gap between the pictures. This makes the pictures merge into each other and we see what appears to be a moving image.

Telecommunications - Summary.

Diffraction of long wavelengths

Diffraction of short wavelengths

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Colour Pictures

Coloured images are seen on a television screen or computer monitor by mixing the three primary colours of light which are red, blue and green. When mixed in equal intensities they produce the following secondary colours:

Mixing Produces

Red and Green light Yellow

Red and Blue light Magenta

Green and Blue light Cyan

Red, Green, and Blue light White

Other colours are produced by varying the intensities of the primary colours.

Diffraction

Diffraction is when waves like light, sound or radio bend around the edge of a barrier. Longer wavelength waves diffract more than shorter wavelengths. Radio for example has a longer wavelength than TV waves so therefore they bend round obstacles like buildings and hills more easily.

Telecommunications - Summary.

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ReflectionReflection can be summarised in the following diagram:

The Law of Reflection states that the angle of incidence equals the angle of reflection.

Angle of reflection

Optical Fibres

An optical fibre is a very thin bundle of glass threads. It works because of total internal reflection. This is when all light is reflected inside the glass and none escapes into the air out with the fibre. This allows light to travel great distances inside the fibre.

Light travels in an optical fibre at about 200 000 000 metres per second.

In an optical fibre transmission system an electrical signal is converted into light by a laser then transmitted down the optical fibre. At the other end it is converted back into an electrical signal by a photodiode. The components work so quickly that hundreds of signals can be transmitted down the optical fibre at the same time.

Telecommunications - Summary.

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Curved Reflectors

Curved reflectors can be used to make a received signal stronger. This is because; The reflector has a larger surface area than the aerial alone and therefore picks up

more waves The detector is placed at the focal point of the dish The waves are reflected from the dish onto the detector A stronger signal is received.

The curved reflector can also be used to transmit a strong parallel beam. The transmitter is placed at the focal point of the dish Waves are directed at the dish and reflect from it The waves are transmitted in a narrow parallel beam.

Telecommunications - Summary.

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Satellites

The time it takes a satellite to orbit the Earth depends on it’s height above the Earth. The higher the satellite the longer it’s orbit. Geostationary satellites take 24 hours to orbit the Earth. This is the same time it takes the Earth to complete one revolution so a geostationary satellite always stays above the same point on earth’s surface.

Signals can be sent from Earth to a satellite using a curved dish transmitter. The satellite also has a curved dish receiver to receive the signal. Once received the signal is made stronger then redirected towards Earth.

If three geostationary satellites were placed above the Earth’s equator, worldwide communication is possible by relaying signals from one satellite to another then back to a different area of the Earth’s surface. This is how a satellite dish on a house receives signals.

Modern Communication Methods

The internet is all of the world’s linked up computers and is what makes the world wide web possible. The internet uses electrical cables, optical fibres, radio waves and satellite links to send information.

The telephone is a method of long range communication. It converts sound directly into electrical signals in the transmitter, which is a microphone, and converts them back into sound in the receiver, which is a loudspeaker. The electrical signals in the wires travel at about 300 000 000 metres per second.

Mobile phones use microwaves to transmit information. Mobile phone networks use “cells” and at the centre of each cell is a base station, the base station sends and receives calls from your phone.

Telecommunications - Summary.

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Wave Properties

Waves carry energy and therefore can be used to transmit signals.

Frequency, f – the number of waves produced (passing a point) each second. Hertz (Hz)

f = N/t

Wavespeed, v – distance travelled by a wave in one second. Metres per second (m/s)

v = d/t

amplitude – size of the maximum disturbance from the central axis. Meters (m)

Wavelength, λ – distance from one point on a wave to the same point on the next wave. Metres (m)

Period , T – time taken to produce a wave. Seconds (s)

T = 1/f OR T = t/N

wavelength

wavelength

wavelength

Amplitude

crest

trough

Central axis

Telecommunications - Summary.

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Wave Patterns

Loud notes have more energy than quiet notes and therefore have a larger amplitude. High pitch notes produce more waves per second and therefore have a higher frequency.

Wave Relationships

Speed, distance and time:

Relationship: distance = speed x timeSymbol: d v tUnit: metres metres per second secondAbbreviation: m m/s s

The Wave Equation:

Relationship: speed = frequency x wavelengthSymbol: v f λUnit: metres per second hertz metresAbbreviation: m/s Hz m

d

v t

v

f λ