Electromagnetic Waves


Summary // Spectrum

Electromagnetic Waves:

  • Can travel through a vaccum
  • Created by vibrating electric and magnetic fields
  • Travel at the speed of light


  • Gamma rays                                     Smallest
  • X rays
  • Ultraviolet
  • Visible light
  • Infrared
  • Microwaves
  • Radio waves
  • Long, medium & short waves             Biggest
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Additive Light // Total Internal Reflection

Additive light                                                   Total internal reflection

(http://t1.gstatic.com/images?q=tbn:ANd9GcS8PR9iTXrAx8XNRo80D52EjBKDZoSEWV5VkTxX0FLDt6-1PbTFZtSPlt_vpg)                           (http://ipodphysics.com/resources/total-internal-reflection.gif)        

                                                                      If light enters at an incident angle more than the                                                                      'critical angle', it is totally internally reflected.

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Visible Light // Infrared Light

Blue filter:

  • Transmits blue (lets blue light through)
  • Absorbs all other colours

Yellow filter:

  • Transmits yellow & green light
  • Absorbs all other colours

Film cameras: Use chemicals to project the image

Digital cameras: Use electrical charges to process the image


Infrared Light:

  • TV remote controls
  • Cameras to detect people in smokey rooms
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Optical Fibres // Radiowaves

Optical fibres:

  • Trap light & information as pulses of light that can be sent along these fibres
  • Can carry more information than electrical wires
  • There is no interference, costs more and absorbs less energy



Producing Radiowaves:

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Radiowaves // Microwaves

  • When the electron moves, waves are created
  • The waves oscillate and reach teh recievers electrons, creating an electrical signel
  • Microwaves can penetrate through the atmosphere and reach satellites. Radiowaves cannot

Microwaves: Used for mobile phones, TV links and satellite TV

Radiowaves (Wavelength > 1m): Used for TV broadcasting, carry more information

Radiowaves (Wavelength between 1m and 100m): Used by radio stations, range is limited

Radiowaves (Wavelength < 100m): Used by national and international radio stations



  • Can beam information from mast to mast
  • Aren't diffracted much by the environment
  • Travel in straight lines
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Doppler effect

Doppler effect:

  • Red shift: Waves are moving AWAY, higher wavelength, lower frequency. Light becomes more reddish
  • Blue shift: Waves are moving TOWARDS, lower wavelength, higher frequency. Light becomes more blueish
  • The larger the red/blue shift, the faster the object is moving(http://www.physicsclassroom.com/Class/sound/u11l3b1.gif)
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Hubble's Discovery/ Big Bang Theory

  • The further away a galaxy, the faster it is moving away from us
  • If everything is moving away from us now, then maybe everything was closer together in the past
  • Maybe everything came from a single point and has been EXPANDING ever since

This is the Big Bang Theory


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Futures of the Universe

CMBR: Cosmic Microwave Background Radiation- the radiation given off by the big bang


Dark matter: this accounts for 90% of the universe's mass ('creating' gravity). Dark matter doesnt give out radiation, so we cannot see it.

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