Electromagnetic Waves

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Electromagnetic radiations are electric and magnetic disturbances.  They travel as waves and move energy from place to place.  All magnetic waves travel through a vacuum at the same speed but they have different wavelengths and frequencies.  All of the waves together are called the electromagnetic spectrum.  We group the waves according to their wavelength and frequency.  Gamma rays have the shortest wavelength and the highest frequency.  Radio waves have the longest wavelength and the lowest frequency.  In order of increasing wavelength and decreasing frequency:

  • Gamma rays
  • X-Rays
  • Ultraviolet radiation
  • Visible light
  • Infrared radiation
  • Microwaves 
  • Radio waves

The spectrum is continuous.  The frequencies and wavelengths at the boundaries are approximate as the different parts of the spectrum aren't precisely defined.  Different wavelengths of electromagnetic radiation are reflected, absorbed or transmited differently by different substances and types of surface.  The higher the frequency of an electromagnetic wave, the more energy it transfers.

All electromagnetic waves travel through space at a wave speed of 300 million m/s.  We can link the speed of the waves to their wavelength and frequency using the equation:

V = f x lambda, where v is wavespeed in m/s, f is frequency in Hz and lambda is wavelength in m.


Visible light is the part of the electromagnetic spectrum that is detected by our eyes.  We see the different wavelengths within it as different colours.  The wavelength increases across the spectrum from violet to red.  ROYGBIV. We see a mixture of all the colours as white light.  Visible light can be used for photography.  Infrared radiation is given out by all objects.  We detect it as heat on our skin, but we can't see it.  The hotter the object, the more infrared radiation it emits.  Remote controls for devices such as TVs use infrared radiation.  Microwaves are used in communications.  Microwave transmitters produce alternating wavelengths that pass through the atmosphere.  They are used to send signals to and from satellites and within mobile phone networks.  Radio waves transmit radio and TV programs and carry mobile phone signals.

Microwave radiation and radio waves penetrate your skin and are absorbed by body tissue.  This can heat internal…


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