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Homework Help: Simple Microscope Problem that I have been STUCK on

  1. Apr 2, 2008 #1
    Simple Microscope Problem that I have been STUCK on!!!

    1. The problem statement, all variables and given/known data
    How far from a lens of focal length 50 mm must the object be placed if it is to form a virtual image magnified in size by a factor of 3?


    2. Relevant equations



    3. The attempt at a solution
    I thought I could us the equation...
    M = s'-f/f to get s' and then use...
    1/f = 1/s + 1/s' to get the object distance

    but I am not coming up with the right answer??
     
  2. jcsd
  3. Apr 2, 2008 #2
    Can anyone help me on this? I still can't get the answer? I am suppose to get 33 mm and I m getting 40 mm
     
  4. Apr 2, 2008 #3

    hage567

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    I don't understand this
    Shouldn't it be just M = -s'/s?
     
  5. Apr 2, 2008 #4
    I don't know its in my book...
    but I don't have s' or s??
    I know F = 50 mm so...
    50 = (1/s + 1/s')^-1
    but I am still not getting it?
     
  6. Apr 2, 2008 #5

    hage567

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    You are trying to find s, right? You were given M so you can solve for s' using the magnification equation and then substitute that into the lens equation which will let you solve for s.
     
  7. Apr 2, 2008 #6
    Ok sooo...
    -s' = ms
    s' = -ms
    1/ms + 1/s = 1/f
    1/s * (1/m + 1/s) = 1/f
    1/s = [(1/f) / (1/m + 1)]^-1 = 66.67??? what am I doing wrong??
     
  8. Apr 2, 2008 #7

    hage567

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    This term should be negative since s' = -ms
     
  9. Apr 2, 2008 #8
    Thank you soooooooooooooooooo much for your help!!!!!!!
     
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