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Homework Help: Image Projection

  1. Feb 25, 2006 #1
    "A 35 mm slide (picture actually 24*36 mm) is to be projected on a screen 1.8*2.7 m placed 9 m from the projector. What focal length lens should be used if the imageis to cover the screen?"

    I was trying to do this problem using the formula (1/do)+(1/di)=(1/f), but hten i realized i dont have the object distance, so what formula can i use?
  2. jcsd
  3. Feb 25, 2006 #2
    There is a formula for magnification? Try if you remember.
  4. Feb 25, 2006 #3


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    Staff Emeritus
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    Try http://hyperphysics.phy-astr.gsu.edu/ this usually gives good information. I believe you assume that object distance, which in this case is the slide, is zero.
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