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Reflection and refraction of light

  1. Feb 9, 2013 #1
    1. The problem statement, all variables and given/known data

    One of the contests at the school carnival is to throw a spear at an underwater target lying flat on the bottom of a pool. The water is 0.900 m deep. You're standing on a small stool that places your eyes 3.20 m above the bottom of the pool. As you look at the target, your gaze is 30 degrees below horizontal. At what angle below horizontal should you throw the spear in order to hit the target?

    Your raised arm brings the spear point to the level of your eyes as you throw it, and over this short distance you can assume that the spear travels in a straight line rather than a parabolic trajectory.

    So, I really am not sure what to do with this problem. Any help with formulas and such would be greatly appreciated. Thanks a lot!!
     
  2. jcsd
  3. Feb 9, 2013 #2

    rude man

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    Draw a picture. Use Snell's law to construct a triangle formed of the incident and refracted rays and your spear's path.
     
  4. Feb 9, 2013 #3
    Just tried that. Not successful. I got an angle of 31 degrees, but that's not right. :(
     
  5. Feb 9, 2013 #4

    rude man

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    Show your work. Preferably show your diagram, otherwise describe it verbally.
     
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