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Homework Help: Light: Geometric Optics

  1. Jul 27, 2011 #1
    1. The problem statement, all variables and given/known data
    A 35mm slide(picture size is actually 24 by 36 mm)is to be projected on a screen1.80m by 2.70 m placed 7.50m from the projector. What focal length lens should be used if the image is to cover the screen?


    2. Relevant equations

    the only equation i can think of is the lens equation which is (1/Do)+(1/Di)=1/f

    3. The attempt at a solution
    I have tried starting this problem numerous times and just have no clue how to start it
     
  2. jcsd
  3. Jul 27, 2011 #2

    ehild

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    Homework Helper

    You need the formula for magnification, too.

    ehild
     
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