use of electromagnetic waves

Question 1

how do mobile phones avoid interference?

Answer 1

each cell sends and receives different frequencies

Question 2

mobile phones:

Answer 2

• they’re used on a system of networks
• mobile phone providers are allocated a band of frequencies in the radio/microwave region
• base stations transmit and receive signals over a limited distance
• frequencies from 800MHz to 2.6GHz are used

Question 3

infrared:

Answer 3

• used in low power devices such as remote controls
• operates over short distances and in ‘line of sight’
• does not work well in bright sunlight
• atmospheric moisture reduces the range of the infrared signal
• a high frequency signal and can potentially transmit large amounts of data
• frequency of around 40KHz

Question 4

wi-fi:

Answer 4

• Wi-Fi allows devices to connect to the internet via a router
• uses medium power in the radio/microwave frequency region
• has a range of up to 100m
• Wi-Fi can pass through walls to allow signals to be received in different rooms in a house
• Wi-Fi signals can also be transmitted through optical fibres and electrical wiring

Question 5

bluetooth:

Answer 5

• bluetooth devices are low powered with a limited range of 10m
• works over short distances
• bluetooth devices can connect to more than one device
• frequency-hopping limits data loss
• uses short wavelength radio signals and does not need ‘line of sight’

Question 6

how does bluetooth avoid interference?

Answer 6

uses a system of ’frequency–hopping’ to reduce interference with Wi-Fi as this uses similar frequencies

Question 7

satellite communication:

Answer 7

• upload and download signals are transmitted at different frequencies
• the signals are high power, transmitted over long distances and in the radio-wave/ microwave region of the electromagnetic spectrum from ground stations
• microwaves can pass through the ionosphere to high orbit satellites
• radio waves are reflected by the ionosphere and so can be used for
  terrestrial communication to receivers beyond the horizon
• radio waves can be used for communication with low orbit satellites
• frequencies from 1 to 40GHz are used

Question 8

what is the process of satellite communication?

Answer 8

signals are transferred from:
uplink antenna -> transponder -> downlink antenna

Question 9

how do satellites avoid interference?

Answer 9

transponders are used to receive, filter out and amplify signals