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Homework Help: Moving the Lens of a Camera

  1. Mar 10, 2008 #1
    1. The problem statement, all variables and given/known data

    http://img368.imageshack.us/img368/9489/physicszv8.jpg [Broken]

    2. Relevant equations

    (1/f) = (1/p) + (1/q)

    3. The attempt at a solution

    I tried solving this but I don't know what the original P was so I can't solve for q. How can I solve this?
    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Mar 11, 2008 #2


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    The focal length is 5cm and the object distance is 100cm. You only have one unknown variable, so it should be easy to solve.
  4. Mar 11, 2008 #3


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    Hi peter!

    In diagram (a), the light rays were parallel, "from a very distant object".

    So the original p was infinity. :smile:

    And 1/infinity = … ? :smile:
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