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Homework Help: Angular Mag

  1. Apr 13, 2008 #1
    1. The problem statement, all variables and given/known data
    f = 10 cm
    i = 25 cm
    Find angular magnification of lens

    2. Relevant equations

    Ang mag = theta_image/theta_object

    3. The attempt at a solution

    I found p to be 16.67
    using 1/p+1/25=1/10

    and I am not sure about the next step.
    theta_0 = atan (16.67/25)
    theta_f = atan (25/25)

    and found thetas, and divided them to get 0.785/0.588=1.335 as my final answer.
  2. jcsd
  3. Apr 14, 2008 #2


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    Homework Helper

    I agree with your object distance...

    But the angular size of an object or image is the tangent of its linear size to its distance from the observer. (You don't want to take ratios of p/f and f/f.) You have no information about the object itself or the size of the image. I think you'll want to use the ratio

    magnification M = -(image distance)/(object distance) .
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