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Lightspeed fast, then slowed, then fast again.

  1. Feb 22, 2005 #1
    I was reading material on light speed and have a question about something I thought may contradict newtons law of conservation of energy.

    Light slows down as it passes through water, glass etc.. right? But when it reaches the other side it continues at light speed. Where is it getting its energy/power supply to continue back at its normal speed? Whats happening here? :eek:
  2. jcsd
  3. Feb 22, 2005 #2


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    It ALWAYS MOVES AT "c"...It's just that matter absorbs it & reemits it and that's why the apparent "slowdown" due to presence of matter...


    P.S.Energy is conserved.
  4. Feb 22, 2005 #3
    ahh, thanks.
  5. Dec 5, 2010 #4
    it never stops moving at "c" :D just the matter makes it slow down, but the nergy is used the same :D
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