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Lenses: If given object height and focal length, is it possible to calculate

  1. May 15, 2005 #1
    the image's height? If so, how? I have the formulas, but see no way of making a substitution.

    If you wanted to know the problem, it states:

    The focal length of a camera is 35 mm and the radius of the moon is 1.74 x 106 m. Calculate the diameter of the moon's image that appears on the camera's film.
  2. jcsd
  3. May 15, 2005 #2


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    Staff: Mentor

    It's impossible to solve the problem using only the given information. However, if you look up the distance between the earth and the moon from somewhere...
  4. May 16, 2005 #3


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    Science Advisor

    Take the moon's distance from the earth to be infinite.
  5. May 16, 2005 #4

    Doc Al

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    Staff: Mentor

    For the purpose of calculating the image distance from the lens, the distance to the moon can be considered infinite. But not for the purpose of calculating the image size on the film.
  6. May 16, 2005 #5
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