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Light interferometry as described in Thorne's black holes and time warps ?

  1. May 25, 2010 #1
    light interferometry as described in Thorne's "black holes and time warps"?


    maybe someone who read the book can help me with this, but i'll give all the information so that even someone who hasn't read it can understand.
    At page 383 and following, and at fig. 10.6 and box 10.3, Thorne describes the basic functioning of a laser interferometric gravitational wave detector. My question is not relative to the "gravitational" part but only to the laser interferometry. In the box and in the figure (link below), Thorne writes that the "waves" reaching the photodetector interfere destructively while the "waves" reaching back the laser/emitter/source interfere constructively. Shouldn't it be the opposite? i was thinking that the "waves" reaching the photodetector, traveling the same distance in space at the same time, (both being reflected twice and passing thru the mirror once), would interfere constructively. Why Thorne writes the opposite instead?
    For anyone who has not access to the book, i found this site which has a picture similar to the one in the book
    it's the drawing rapresenting laser interferometry. In the book Thorne writes that there should be no light in the photodetector due to destructive interference. Why it is not the opposite (all the light in the photodetector due to costructive interference)?
    Last edited: May 26, 2010
  2. jcsd
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