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Conservation of Energy Problem

  1. Dec 5, 2009 #1
    There is an interesting article here

    http://focus.aps.org/story/v18/st4

    about a method for tunnelling light through usually opaque materials. Half way through they mention that one light ray becomes two:

    "When a light ray passing from glass into air strikes the interface at a sufficiently shallow angle, it reflects entirely back into the glass with no transmission into the air. In this effect, known as total internal reflection, some of the electromagnetic field strays across the boundary between the two materials as a so-called evanescent wave, which carries no energy away. But if the evanescent wave encounters another block of glass a short distance away, a true light wave with reduced intensity appears in the second block."

    I am interested to know where the extra energy for the second light wave comes from, and is this a good way of building a power station, cycling the energy through the system and getting apparently more out each time.
     
  2. jcsd
  3. Dec 5, 2009 #2
    I am not a physicist; not even close to it. so excuse me if I am telling stupid thing but right the next paragraph says that:
    "This optical phenomenon is mathematically identical to the quantum tunneling of a particle through a classically insurmountable barrier."
    If my logic does not betray me, the energy comes from the similar source as for the particle tunneling through the barrier.
    The text you copied above, does not mention if the internal reflection is still total if the mentioned evanescent wave encounters another block of glass.
     
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