P1.5 WAVES 2

P1.5 WAVES 2

1. ELECTROMAGNETIC SPECTRUM

   • TRANSVERSE waves
   • All types of electromagnetic waves travel at the same speed through a vacuum (space) 3*10(8)m/s
   • Electromagnetic waves form a continuous spectrum.
   • Wavelengths vary from about 10 (–15)-Gamma- metres to more than 10(4)-radio- metres.
   • Gamma= high frequency, shorter wavelength, high energy
     • Granny's Xbox Uses Volts In My Room
   • Radio= low frequency, longer wavelength, low energy

2. RADIO

   • mainly used for communication
   • long-wave radio wavelengths can be transmitted from London & received half way across world because long wavelengths diffract around the curved surface of the earth
   • long-wave radio wavelengths can diffract around hills, into tunnels etc
     • this diffraction effect makes it possible for radio signals to be received even if the receiver isnt in like of sight of the transmitter
   • short wave signals reflect off the ionosphere
     • radio waves used for TV & FM radio transmissions have very short wavelengths can be
   • long wave signals diffract around the earth

3. MICROWAVES

   • used for SATELLITE COMMUNICATION & MOBILE PHONES
   • Microwaves easily pass through the earth's watery atmosphere (radiowaves cannot do this)
   • phone calls travel as microwaves between ur phone & the nearest transmitter.
   • Some wavelengths are absorbed by water molecules that heat them up
     • so people think that the cells in ur brain may start to cook
       • no conclusive evidence
       • but may be long term effects that we dont know about

4. INFRARED

   • used for: REMOTE CONTROLS & OPTICAL FIBRES
   • remote controllers work by emitting diff patterns of infrared waves to send diff commands to an appliance
   • Optical fibres use both infrared waves and visible light
     • can carry data over long distances quickly
       • pulses of light/ infrared radiation is reflected off the sides

5. VISIBLE LIGHT

   • used for PHOTOGRAPHY
   • cameras use lens to focus visible light onto a light sensitive film or electronic sensor