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Does a light pulse get amplified when it goes to a less dense medium?

  1. Jan 16, 2010 #1
    Since a string pulse get amplified when it enters a less dense medium such as from the thick heavy rope to a lighter string, why does not light do the same?
  2. jcsd
  3. Jan 16, 2010 #2
  4. Jan 16, 2010 #3
    Come to think of it, there is a medium and the medium is the electromagnetic field.
  5. Jan 16, 2010 #4
    It never goes to a "different medium".
  6. Jan 16, 2010 #5
    When light goes from a medium such as glass (index of refraction n=1.5) to air, about 4% of the energy is reflected, and 96% of the energy is transmitted. The ratio of the transverse E (electric) vector to the transverse H (magnetic) vector in light is proportional to 1/n, so the ratio E/H increases when the light goes from glass to air. But the transmitted energy decreases by 4%. So the amplitude E increases, but the transmitted energy, which is proportional to E times H (Poynting vector), decreases.
    Bob S
  7. Jan 16, 2010 #6
    Thanks, Bob!
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