Physics P1 6.3 Communications.

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What are radio waves of different frequencies used for?
Different purposes.
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What are used for satellite TV signals?
Microwaves.
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What is needed to evaluate whether or not mobile phones are safe to use?
Research.
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What are optical fibres?
Very thin glass fibres that are used to transmit signals by visible light and infrared radiation. The signals travel down the fibre by repeated total internal reflection.
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What does an alternating voltage apple to an aerial emit?
Radio waves with the same frequency as the alternating voltage. When the waves are received they produce an alternating current in the aerial with the same frequency as the radiation received.
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What is the radio and microwave spectrum divided into?
Different bands.
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What are the different bands in the radio and microwave spectrum used for?
Different communications purposes.
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How is communication affected by wavelength?
The shorter the wavelength of the waves the more information they carry, the shorter their range, the less they spread out.
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How do mobile phones communicate?
With a local mobile phone mast using wavelengths just on the border between radio waves and microwaves, they are usually referred to as microwaves.
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Why do some scientists believe mobile phones may be harmful?
Some scientists think that the radiation from mobile phones may affect the brain, especially in children.
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How are optical fibres carrying visible light or infrared useful in communications?
They carry much more information and are more secure than radio wave and microwave transmissions.
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How are radio waves produced?
By applying an alternating voltage to an ariel.
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**LOOK UP FIBRE OPTIC CABLES**
*
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Other cards in this set

Card 2

Front

What are used for satellite TV signals?

Back

Microwaves.

Card 3

Front

What is needed to evaluate whether or not mobile phones are safe to use?

Back

Preview of the front of card 3

Card 4

Front

What are optical fibres?

Back

Preview of the front of card 4

Card 5

Front

What does an alternating voltage apple to an aerial emit?

Back

Preview of the front of card 5
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