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Ray Diagram

  1. Mar 31, 2009 #1
    1. The problem statement, all variables and given/known data

    I'm supposed to quantify the picture below and show how to find D and the angle theta.

    http://img10.imageshack.us/img10/7079/labg.jpg [Broken]

    2. Relevant equations

    none i can think of

    3. The attempt at a solution

    I guess S and H are the same. I really can't think of a way to find D or theta though. Don't you need D to find theta?
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Mar 31, 2009 #2

    rl.bhat

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    Opening of the camera, object and image from two similar triangles. Their sides are proportional.
    Length of the camera and film height are known quantities. From that find D and theta.
     
  4. Apr 1, 2009 #3
    Alright so my camera's length is 14.6cm and the film height is 5cm. Even if I know they're proportional how can i find D?
     
  5. Apr 1, 2009 #4

    rl.bhat

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    To find D you must know H. As your guess S need no be equal to H.
     
  6. Apr 1, 2009 #5
    Alright well we aren't given H so how would I theoretically get H?

    Would I do 5/14.6 = h/d? And after I find D how would i find theta?
     
  7. Apr 1, 2009 #6

    rl.bhat

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    You can find theta. 2.5/14.6 = tan(theta/2). But that won't give you D unless you know the size of the object.
     
  8. Apr 1, 2009 #7
    Alright but even if i know my H, isn't the theta different? lets say my H is 7.5 cm. I got theta/2 for the left triangle to be 4.86 degrees. Where do I go from there though?
     
  9. Apr 1, 2009 #8

    rl.bhat

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    Yes. For same H theta depends on D. When D changes size of the image also changes.
    Theta will be unique only for one setting.
     
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