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Homework Help: EM Waves and Refraction

  1. Mar 23, 2005 #1
    I am doing a science fair project on refraction and I am preparing for the regionals and I found a small flaw in my report and I am wondering if any of you guys can help me out here.

    This is what I wrote:

    Why do electromagnetic waves warp when it goes through the process of refraction? The reason lies in the subatomic level of science. First of all, an electromagnetic wave is produced by a vibrating electric charge. As it traverses through a vacuum of space, it travels in a velocity of 2.99792458 x 108 m/s, or can be expressed as ā€œcā€. When the wave collides with a particle of matter, the wave is absorbed and the electrons within the atoms undergo a vibrating motion. If the frequency of the electromagnetic wave is not identical to the frequency of the vibrating electron, the energy is reemitted in a form prior to absorption, as an electromagnetic wave.
    The new wave will have identical frequency as the previous wave and it will also travel through the trans-atomic space until it confronts another atom. If the frequencies are different, the electrons will go through a vibrating motion once again. This cycling process continues until the electromagnetic wave is transported through the medium.
    This process is the fundamental cause of slowing down the velocity of an electromagnetic wave. Every photon in the electromagnetic wave travels the trans-atomic space at c, but the process of absorption slows it down. Therefore, the overall speed of an electromagnetic wave traversing any substance will have less speed as it would travel in a vacuum.

    What I fear is, when the frequency between the EM wave is indeed identical to the frequency of the vibrating electron.. what happens then? I bet you 2 bottles of scotch that the judges will ask me that :biggrin:

    Any assistance would be more than greatful.
    Thank you very much :smile:
  2. jcsd
  3. Mar 23, 2005 #2
    I think where you went wrong is
    Realize that the matter STARTS vibrating when the photon hits it. If the matter had really small density (like in space) then the light would not slow down at all, but if the matter does have a reasonable density, then the light will slow down more as density increases.

    For example, the density of air is 1.2 kg/m^3 whereas the density of water is about 1000 kg/m^3. Thats why light travels much faster in air (2.8 x 10^8 m/s) than in water ( 2.2 x 10^8 m/s).
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