EM Waves and Communication

EM Waves and Communication

1. Infrared, Microwaves, Radiowaves

   • Infrared
     • TV remote
     • Night vision cameras
   • Microwaves
     • Communication signals
       • Mobile phone
       • Satellite
   • Radiowaves
     • TV and radio transmission
     • Radar

2. Long Distance

   • Radiowaves and Microwaves
     • Not absorbed by atmosphere
   • Radiowaves
     • TV and radio signals
       • Much shorter wavelength than normal radiowaves
   • Microwaves
     • Mobile phone communciation
       • Much longer compared to normal
         • Still tiny compared to radiowaves

3. Microwaves

   • Pass easily through atmosphere
   • E.g. satellite TV
     • Transmitter transmits signal to space
       • Absorbed by satellites
         • Orbit thousands of kilometers above Earth
         • Transmit signal back down to Earth
           • Different directions
           • Received by satellite dish
             • Sides reflect radiation to focus at receiver
               • Made of metal

4. Optical fibres

   • Infrared and visible light
   • Waves bounce off sides of thing inner core
     • Made of plastic or glass
       • Signal won't weaken as don't absorb much radiation
     • Keep reflecting off until reach the other end