Why are radio waves and microwaves good at transmitting information over long distances?
Because they are not strongly absorbed by the atmosphere.
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What wavelengths do microwaves used for mobile phones use?
Very long wavelengths compared to most microwaves
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What wavelengths do radiowaves used for TV and FM radio use?
Very short wavelengths compared to most radiowaves
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What carries information along optical fibres and why?
Light and infrared radiation because the radiation travels large distances through glass without much being absorbed so does not weaken
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How do optical fibres work?
Waves repeatedly bouncing (reflecting) off the inner core of the glass
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How is a signal created?
Information is converted into electrical signals and then mixed (superimposed) onto an electromagnetic carrier wave and then sent out as a analogue or digital signals.
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What is an analogue signal?
A signal which can vary continuously
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What is a digital signal?
A signal that can take only a small number of discrete values (usually two)
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How can sound and images be transmitted?
As a digital signal
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In digital transmission what is the digital code made up from?
Just two symbols, ‘0’ and ‘1’
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How can digitally coded information be carried?
By switching the electromagnetic carrier wave off and on to create short bursts of waves (pulses) where ‘0’ = no pulse and ‘1’ = pulse
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What happens when the waves are received?
The pulses are decoded to produce a copy of the original sound wave or image
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Why do signals have to be amplified?
Both analogue and digital signals weaken as they travel
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What are the advantages of digital signals over analogue signals?
If noise has affected the original signal this is less of a problem with digital signals as they are either 0 or 1 and so can be recovered more easily than analogue signals.
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What is the amount of information needed to store an image or sound measured in?
Bytes (B)
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How is the quality of a sound or image increased in digital signals?
Higher quality signals send more information by sending several signals at once
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What is an advantage of using digital signals?
The information can be stored and processed by computers
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Other cards in this set
Card 2
Front
What are microwaves used for?
Back
Mobile phones and satellite communication
Card 3
Front
What are radio waves used for?
Back
Card 4
Front
Why are radio waves and microwaves good at transmitting information over long distances?
Back
Card 5
Front
What wavelengths do microwaves used for mobile phones use?
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