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Unit 3.3 Telecommunications
Page 145


7. Complete the map with the correct words.

WIRELESS TRANSMISSION

Features:
• 1. : size of wave from highest to lowest point
• wavelength: 2. between two waves from same 3.
• frequency: 4. of waves passing a point in certain time
• crest: 5. point of wave
• 6. : lowest point of wave

Use:
Electromagnetic waves belong to the electromagnetic 7. , the range of waves according to wavelength and 8. . The electromagnetic waves usually included in wireless transmission are:
• microwaves: 9. communication
• 10. waves: remote controls
• visible light: 11. optic communication + TV transmission of images

Applications:
• mobile networks: distributed over 12. → wide 13. coverage
• Bluetooth technology: low frequency 14. waves
8.1 Say if the sentences are true (Vero) or false (Falso).
1. Electromagnetic waves are produced by the oscillation of an electromagnetic charge.
2. The amplitude of a wave is the distance from any point on one wave to the same point on the next.
3. The wavelength is measured in Hertz.
4. The frequency is the number of waves passing a point in a certain time.
5. The trough is the lowest point of a wave.
6. The waves of an electromagnetic spectrum are arranged according to frequency and amplitude.
7. Radio and TV communications use only infrared waves.
8. Remote controls generally use microwaves.
9. In mobile networks, several cells linked together cover a large geographical area.
10. The frequency used by Bluetooth technology cannot reach a distance over 50 metres.
8.2 Correct the false sentences from the previous exercise. aperta
9.1 Watch the video and match each wave with its characteristics.
They include all the parts which make up a rainbow.They can easily penetrate matter.They are reflected off the ionosphere.Insects can see them.They generate heat by making molecules vibrate.They represent the first part of the spectrum that animals can detect.
Radio →
Microwaves →
Infrared →
Visible →
UV →
X-rays and gamma rays →
9.2 Watch the video in the previous exercise and match each wave with its uses.
Telecommunications.Human sight.Remote controls.Fluorescent lamps for tanning.Medicine.To cook food and also in satellite communications.
Radio →
Microwaves →
Infrared →
Visible →
UV →
X-rays and gamma rays →