Saturday, February 12, 2011

Electromagnetic (EM ) waves

Electromagnetic wave is a self-propagating wave in space with electric and magnetic components.

These components oscillate at right angles to each other and to the direction of propagation, and are in phase with each other.
Electromagnetic wave is classified into types according to the frequency of the wave:
these types include ( order of decreasing frequency)

gamma rays, X-rays, ultraviolet radiation,visible light, infrared radiation, microwaves and radio waves.

source :

Nature of EM wave:

  1. Show characteristics of polarisation.
  2. transverse wave.
  3. since EM waves are transverse wave it do not require a medium to propagate and can travel in vacuum.
  4. EM wave still a wave so energy is transferred by the wave.
  5. obey the wave equation v = f λ .
  6. in a vacuum, the waves travel at the speed of light c = 3 x 10 8 ms -1
  7. undergo reflection, refraction, diffraction and interference .
  8. electrical neutral.

Examples of some uses of electromagnetic waves :
  1. Gamma rays - sterilisation of equipment.
  2. X-ray - radiography ( X-ray photograph )
  3. ultraviolet - identification of counterfeit notes.
  4. Visible light - sight
  5. infrared - night vision, thermal imaging .
  6. microwave - cooking, radar system , satellite transmission ( example : Astro satellite TV, GPS..)
  7. Radio waves - telecommunication , communication.

1. Explain how an EM wave propagates, with the aid of a diagram.
2. What is the speed of light? What symbol is used to refer to the speed of light? Does the speed of light change?
3. Do EM waves need a medium to travel through?


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