Flashcards
Wireless Signals
Cards in this deck (11)
- 1What can electromagnetic radiation (such as microwaves and radio waves) be used as, why is this good, but what is a disadvantage?It can be used to send information without optical fibres because it can be reflected and refracted in the same way as visible light. Sometimes this is a disadvantage because it can cause loss of signal.
- 2What are the three main advantages to wireless technology?Wireless technology is used in TVs, radios, mobile phones and laptop computers.
The three main advantages are:
No wiring is needed - you don't need to be connected directly to the transmitter.
It enables items to be portable and convenient.
It allows access signals on the move. - 3What does long-distance communication depend on?Reflection - the ionosphere is an electrically charged layer in the Earth's upper atmosphere. Longer wavelength radio waves are reflected by the ionosphere. This enables radio and television programmes to be transmitted between different places, which may be in different countries or continents around the Earth.
Refraction - at the interfaces of different layers of the Earth's atmosphere, refraction of waves results in the waves changing direction. - 4How does the ionosphere work in the same way as total internal reflection?Refraction and reflection in the ionosphere act in the same way as total internal reflection for light and keep the signals in the Earth's atmosphere instead of escaping into space.
- 5What are the negative effects on wireless signal quality?Diffraction - at the edge of transmission dishes causes the waves to spread out, which results in signal loss. Interference from similar signals limits the distance between transmitters. Positioning transmitters in high places can help to overcome the nuisance of obstacles blocking signals.
Refraction - at the interfaces of different layers of the Earth's atmosphere can lead to loss of signal. - 6How can signals be sent by satellites above the atmosphere?If signals are sent to satellites above the atmosphere, the signals can be 'bounced' from satellite to satellite (received and transmitted) to cover longer distances and travel round the world.
- 7What is interference, and what are the different forms?Some signals have a poorer quality than others so sometimes the information is 'noisy' and you get hissing, called interference. Another form of interference can happen if there are two radio stations using similar frequencies. The two stations can cause mutual interference so that you hear parts of one program on top of another.
- 8When can interference not happen?It cannot happen with digital signals because each station has a transmission frequency that is well separated from all the others (each station requires less bandwidth so there is more space) and the processing enables random signals to be filtered out before they are turned into sound or light.
- 9What does DAB stand for, and what do analogue signals suffer from?Some radio stations provide better signals than others. Analogue signals suffer from interference. DAB (Digital Audio Broadcasting).
- 10What are the advantages of DAB?More stations can be transmitted.
There is less interference between stations. - 11What are the disadvantages to DAB?The audio quality is poorer than FM (frequency modulated signals, analogue).
Not all areas of the country are covered so you may be driving along and pass into an area where there is no signal.
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- GCSE Physics (P1) Flashcards on Wireless Signals, created by Rebecca Smith on 06/11/2016.
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- Rebecca Smith
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