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Homework Help: Lenses and optics: solving for focal point.

  1. Apr 27, 2009 #1
    Lenses and optics: solving for focal point. (SOLVED)

    (2 points, penalty of 0.5)
    When a flower pot is placed 1.2 meters on the left of a magnifying glass (converging lens), an image is formed on a screen 0.37 meters to the right of the lens. Find the focal length of the lens. Give your answer ...

    * in terms of meters. Do not include units in your answer. They will be assumed to be meters.
    * to a precision of hundreths of a meter. Use a format like #.## in your answer.
    * to an accuracy of 0.02 m. Answers within 0.02 meters of the correct answer will be tolerated.

    I know that with a converging lens, the focal point value will be positive.
    I started with the basic equation
    1/f = 1/do + 1/di

    1/f = 1/1.2m +1/.37m
    f = .833333333m + 2.7027m

    f = 3.536 m
    I entered this value and it counted it as incorrect. can somebody please tell me what i'm doing wrong? i would appreciate it. thanks ! :redface:http://moodle.oakwood.k12.oh.us/file.php/72/Unit_13_quiz_images/quiz13q3.jpg
    Last edited by a moderator: Apr 24, 2017
  2. jcsd
  3. Apr 27, 2009 #2


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    Homework Helper

    f = 3.536 m
    This should be
    1/f = 3.536
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