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Objectives

Be able to describe how radio waves are used in communications.

HSW: AF2: Evaluate the effects of technological developments on society as a whole. Used before in: Will use again in:

PLTS: Team Workers: collaborate with others to work towards a common goal.

Used before in: Will use again in:

18 April 2023

KeywordsEM Spectrum, Radio, Frequency, Wavelength, Diffraction, Reflection, Refraction, Interference, Ionosphere Ghosting.

Radio Waves

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Outcomes

All students should be able to: • Describe communications devices that

use radio waves.Most students should be able to: • Describe how radio waves are used in

communications and how we can transmit radio waves large distances.

Some students should be able to:• Evaluate the safety of using radio waves

to communicate.

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Which is the odd one out?

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What are radio waves?

The broadcast of every radio and television programme involves the use of radio waves.

Radio waves are the type of electromagnetic waves with the longest wavelengths.

Radio waves have a wavelength greater than 30 cm (the length of a standard ruler).

Radio waves have many uses. How many can you think of?

micro-wavesradio waves infrared

1000 m 1 mm1 m 0.001 mm

ultra-violet

wavelength of electromagnetic waves

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How are radio waves produced?

Radio waves are produced by passing an oscillating electric current through a long wire called an aerial.

The frequency of the radio wave produced is the same as the frequency of the oscillating current.

This allows radio waves of different wavelengths to be produced.

These radio waves have slightly different properties and are used for different purposes.

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What are radio waves used for?

Broadcasting Radio waves of different frequencies are

used to broadcast radio and television. Communications

Several types of radio waves are used for communications. e.g. Bluetooth and WiFi

Radio control Radio waves can be used to send signals

to control model cars, planes and boats. Radio frequency identification

This identification system involves tagging an object, animal or person with a microchip that responds to specific radio frequencies. It can be used to identify pets and keylesslocks on doors.

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What is a wave?

• Can be reflected

• Can be refracted

• Can be diffracted

• When 2 waves overlap they superimpose on each other and this can cause interference.

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Why is my TV reception poor?

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Why is my radio reception poor?

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Can radio waves travel through walls?

Radio waves are not absorbed strongly by walls, which is why radio (and television) signals can be received indoors.

Tall objects, like buildings and hills, can prevent radio waves travelling directly from a transmitter, but this is not always a problem.

In some areas, the reflection of waves off other buildings or hills can actually lead to improved radio reception.

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How can we get long-distance radio communication?By reflection and refraction in the atmosphere

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Effect of the atmosphere – simplified

IonosphereSome frequencies

reflect here ...

Earth

...so radio signals can be picked up here

Some radio waves follow curved paths due to

refraction

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Why do some radio waves travel far?

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Radio waves

Radio waves are produced by passing an ………… electric current through a long wire called an ……... The …………. of the radio wave produced is the same as the ………….. of the oscillating current. This allows radio waves of different ………….. to be produced. When 2 waves overlap they ………… on each other and this can cause …………...

Oscillating aerial frequency Ionosphere superimpose refraction reflect signals wavelengths interference

………………….

Some frequencies ………. here.

Earth

...so radio ………. can be picked up here

Some radio waves follow curved paths due to

………………

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Big Q: Is WiFi Safe?

• Watch these 2 youtube clips and answer the questions your teacher will give out. Then come up with your own opinion about the risks of WiFi:

• http://www.youtube.com/watch?v=C5OuxG6l4X4

• http://www.youtube.com/watch?v=8Hi4NmQEsdg&feature=related

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The Big Q: Is WiFi safe?

• For • Against

I think that WiFi is / is not safe because ….

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Just a Minute - Communicating with Radio Waves

• You must talk about Communicating with Radio Waves for one minute.

• You mustn’t hesitate, deviate from the topic or repeat yourself.

• If you do you may be challenged – if successful that person carries on from the time they challenged.

• Whoever is speaking when one minute is up is the winner.