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Interference/Diffraction with shadows

  1. Sep 25, 2008 #1
    1. The problem statement, all variables and given/known data
    At 11:00hrs a vertical stick in air, 1.8 m long, casts a shadow 1.2 m long. If the same stick is placed at 11:00hrs in air in a flat bottomed pool of salt water half the height of the stick, how long is the shadow on the floor of the pool? (For this pool, n = 1.56.)

    2. Relevant equations
    Not sure=/

    3. The attempt at a solution
    Don't know where to begin >.<
  2. jcsd
  3. Sep 25, 2008 #2


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    sounds like more of a *refraction* problem than an interference/diffraction problem. In other words, I think you can do this problem using only geometric optics, without considering the wave nature of light.

    So, ask yourself, what *happens* to a ray of light upon entering the water that would tend to change the nature of the shadow cast by the stick? Strong hint: the length of the shadow is determined by the angle of the light source.
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