Electromagnetic waves and communication

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  • Created by: jaaaz_v
  • Created on: 11-06-15 22:14
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  • EM Waves and Communication
    • Radio waves
      • Wavelengths longer than around 10cm
      • Long wavelengths diffract around the curved surface of the earth
        • So can be transmitted to all over the world
        • Can also diffract around hills and tunnels
      • Diffraction makes it possible for the radio signals to the receiver even if they're not in sight of the transmitter
      • The waves used for TV's and radio have short wavelength
        • To get reception you must direct sight of the transmitter
        • signal doesn't bend around hills or go through buildings
    • Microwaves
      • Used for communication to and from a satellite
      • Signal from a transmitter is transmitted into space where its picked up by the satellites receiver dish
        • Satellite then transmits the signal back onto earth
          • Where its received on a satellite dish
      • Some wavelengths of microwaves are absorbed by water molecules and heat them up
        • Could damage our cells if we use the phone too much
    • Infrared waves
      • Used in wireless remote controllers
      • Remote controls work by emitting different patterns of infrared waves to send different commands to an appliance
      • Optical fibers use both infrared waves and visible light to carry data over long distancs quickly
        • Signal is carried as pulses of light or infrared radiation and is reflected off the sides of the fiber
    • Visible light
      • Used for photography
      • Cameras get the lens to focus visible light onto a light sensitive film or sensor
    • EM Waves
      • Have different wavelengths and so have different properties
      • Different types of EM waves travel at the same speed
      • Waves with higher frequencies have shorter wavelengths


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