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SCIENCE FORM 5

CHAPTER 8: ELECTRONICS AND INFORMATIONAND COMMUNICATION TECHNOLOGY (ICT)


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8.1 RADIO WAVES

Wavesthat cause particles in a medium to

vibrate perpendicularly to the direction

in which the waves travel are calledtransverse waves.

Examples of transverse waves:

(i) Water waves

(ii) Electromagnetic waves


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8.1 RADIO WAVES

Transverse wave


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8.1 RADIO WAVES

Characteristicsof waves

Amplitude, A- Maximum

displacement of awave from its restingposition

- SI unit is metres (m)

Wavelength,

- Distance between twosuccessive crests or

troughs

- SI unit is metres (m)

Frequency, f

-Number of crestsor troughs that

passes through apoint per second

- SI unit is hertz(Hz)

Wave velocity,v

- Distance travelledby the wave in one

second

- SI unit is metresper second (m/s)


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8.1 RADIO WAVES

Characteristics of a transverse wave


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8.1 RADIO WAVES

All electromagnetic wavescan travel in

a vacuum.

The electromagnetic spectrumis therange of all electromagnetic waves.


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8.1 RADIO WAVES

Electromagnetic spectrum

Radio Music In Victoria University X Games


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8.1 RADIO WAVES

Characteristicsof

electromagneticwaves

All are transversewaves

Can travel in vacuum

Moves very fast


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8.1 RADIO WAVES

Radio communication

As the Earths surface is curved, radio

waves cannotbe transmitteddirectlyover long distances without being

blockedby the Earths surface.

For long distance communication usingmedium or long waves, relay stations

are used to extendthe rangeof

transmission.


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8.1 RADIO WAVES

For long distance communication using

short waves, short waves are first sent up

to the ionospherewhere they arereflected back to a receiveron Earths

surface.


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8.1 RADIO WAVES

Relay stations are used to extend the range of transmission of medium or long waves


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CHAPTER 8.1 RADIO WAVES

Short waves are reflected by the ionosphere back to the Earth


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8.1 RADIO WAVES

Television broadcasting

Most television broadcasting uses

VHFs or UHFs.The television stations inMalaysia uses

UHFsto broadcast their programmes.


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8.1 RADIO WAVES

Satellite communications

Satellite communications involve the

transmissions of information in the form ofmicrowavesbetween the satellitesand

the Earth.

Most satellites receive signalsfromEarth, strengthenthe signalsand then

send the signals backto Earth.


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8.1 RADIO WAVES

Satellite communication


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8.2 RADIO COMMUNICATION

Electronic

component

Symbol Function

Aerial To receive all radio waves with

different frequencies within its

range

Inductor Works with a variable capacitor to

form a tuning circuit

Variable capacitor Works with an inductor to form a

tuning circuit

Diode Separate the a.f. signals from the

the amplified modulated r.f. signals

through modulation

Capacitor To store electric charges


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Electronic

component

Symbol Function

Transistor To amplify the a.f. signals before

sending them to the loudspeakers

or earphonesResistor Works with a transistor to amplify

the a.f. signals

Transformer To change the voltage of an

alternating current


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The radio transmission system

Sound waves cannot travel very far

through the air. So a radio transmissionsystem is needed.


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Sound waves areconverted into electricalsignals known as audiofrequency signals (a.f.

signals) by a

microphone

The a.f. signals are sentto an amplifier where

their amplitude isincreased

The amplified a.f. signalsare sent to the modulator.

At the same time anoscillator generates radio

waves known as radiofrequency (r.f.) carrier

waves which is also sent tothe modulator

In the modulator, the a.f.signals combined withthe r.f. carrier waves

through amplitudemodulation (AM) or

frequency modulation(FM) to produce

amplitude modulated r.f.signalsor frequency

modulated r.f. signals

Modulated r.f. signalsare finally sent to atransmitting aerialwhich converts the

modulated r.f. signalsinto radio waves

The radio waves aretransmitted at a

particular frequencyfrom the transmitting

aerial to its surrounding


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Modulator

r.f. oscillator

Electrical

power supply

A radio transmitter

Sound waves

Microphone

Amplifier

Amplified a.f.

signals

Amplitude

modulated r.f.

signals (r.f.

signal carrying

a.f. signal)

Radio waves

transmitted at

one frequency

r.f. signals

a.f. signal


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The radio receiver system

In the radio receiver system, a receiving

aerial receives the weak radio waves withmany frequencies transmitted from

different radio stations.


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All weak radio wavesare received by the

receiving aerial

The radio waves areconverted back into

modulated r.f.signals with different

frequencies which arethen sent to thetuner

At the tuner, thefrequencyof the radioreceiver is adjustedtomatch thefrequency of

the radio station

When the frequency ofthe radio receiver

matches the frequencyof the required radio

station, the modulatedr.f. signalsbecome

stronger by having alarger amplitude

The strongermodulated r.f.

signals are thenpassed through an

amplifierwhere theiramplitudeisincreased

The amplifiedmodulated r.f. signalsare sent to a detectorwhich separates thea.f. signals from the

modulated r.f. signals(demodulation). The

a.f. signals areamplified

The amplified a.f.signals are sent to aloudspeaker which

converts them back tosound waves. The

sound waves are thentransmitted at differentfrequencies from the

loudspeaker to itssurrounding


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Tuner

Electrical

power supply

A radio receiver

Radio waves

of different

frequencies

Amplifier

Receiving

aerial

Weak r.f. signals

of different

frequencies

Amplified r.f.

signals

Detector

Selected r.f.

signal (one

particular

station)

a.f. signal

separated from

the r.f. signal

Amplifier

Amplified a.f.

signal

Loudspeaker


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8.3 SATELLITE COMMUNICATION

Microwave signals used for satellite

communication system have very high

frequencies.

At a ground station on Earth,microwave signals of certainfrequency are sent up to acommunication satellite

The communication satelliteamplifiesthe microwavesignals and convert it to

another frequency

The amplified microwave

signals are sent to satellitedishes or other groundstations


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Advantagesof using

satellites totransmit

information

A wide coveragefor the

transmission ofsignals

Clear signalstransmitted

without beingcorrupted

Signalstransmitted at the

speed of light

Low cost ofsending

information overlong distances


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Other uses ofsatellites

Navigation

Exploration Surveillance

Weather


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8.4 THE IMPORTANCE OF USING ICT FOR THE

BENEFIT OF MANKIND

The useof ICThas greatly benefited us

in many different ways. ICT allows us to

communicate over long distances bysending information in various forms such

as text, pictures, sounds and videos in

great volumes and at high speeds.


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CHAPTER 8: ELECTRONICS AND INFORMATION AND

COMMUNICATION TECHNOLOGY (ICT)

QUIZ

1. The diagram shows a wave form.

What is the wave length of the wave?

A. 2 m B. 4 m

10 m

20 m


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QUIZ

2. Which propagation wave has the highest

frequency?

A.

B.

C.


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QUIZ

3. A wave with a frequency of 50 Hz moves

at a velocity of 300 ms-1. What is the

wavelength of the wave?A. 6 m B. 250 m

C. 350 m D. 1500 m


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QUIZ

3. A wave with a frequency of 50 Hz moves

at a velocity of 300 ms-1. What is the

wavelength of the wave?A. 6 m B. 250 m

C. 350 m D. 1500 m


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QUIZ

4. Which of the electronic components A, B,

C or D is able to store charges?

A.

B.

C.


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QUIZ

5. Which of the following electric

components allows current to flow in one

direction only?A.

B.

C.

D.


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QUIZ

6. A radio could not receive a broadcast

clearly. Which part of the radio receiver

should be modified?A. Diode B. Aerial

C. Speaker D. Transistor


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QUIZ

7. What is the symbol of a resistor?

A.

B.

C.

D.


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QUIZ

8. What is the function of the microphone in

a radio transmitter?

A. Receives radio wavesB. Generates radio waves

C. Converts sound waves to electrical

signals

D. Combines carrier waves and sound

signals


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QUIZ

9. Which of the following is true about

communication satellites?

A. Located outside the Earths orbitB. Obtains energy from the Earths

satellite station

C. Three satellites are needed forworldwide communication

D. Makes one complete orbit around the

Earth in one month


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QUIZ

10. What is the use of communication

satellites?

A. ArchaeologyB. Weather forecast

C. Radio broadcasting

D. Wireless microphone


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