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Homework Help: Two lens systems

  1. Jul 5, 2010 #1
    1. The problem statement, all variables and given/known data
    Two Lens systems:
    Lens one is a diverging lens and lens two is converging

    O1 (object distance) = 9.6 cm
    Focal length F1= 6.5 cm
    distance between the two lenses is 13 cm
    F2 = 7.4 cm
    Find the image distance i2 for the image produced by lens 2 (the final image produced by the system) and the overall lateral magnification M for the system, including signs.


    2. Relevant equations

    1/i + 1/o = 1/f

    3. The attempt at a solution

    i1 = 20.13 cm
    o1=9.6 cm
    i2=
    o2=1/

    i1
    (1/6.5) - (1/9.6) = 1/i = 0.049

    i1 = 20.129

    o2
    d = 13 cm
    o2 = d - i1 :confused:
    o2 = 13 - 20.129
    o2 = -7.129 cm

    i2

    1/i =(1/7.4) - (1/-7.129)
    i2 = 3.63 cm


    Anyways I keep getting this incorrect but I am not sure what is wrong I think I mess up solving for the object2 but I have no idea.
     
  2. jcsd
  3. Jul 5, 2010 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Where is the image from lens 1 alone? Show how you'd calculate that.
     
  4. Jul 5, 2010 #3
    Hello neophyte,for your diverging lens the focal length should be given a negative value and for your converging lens it should be given a positive value.
     
  5. Jul 5, 2010 #4
    -(1/f) - (1/O) = (1/i)
    -(1/6.5) -(1/9.6) = 1/i = 0.258

    i1 = -3.87




    :redface:

    d = 13 cm
    o2 = d - i1
    o2 = 13 +3.875
    o2 = 16.875 cm


    1/i2 = (1/f) - (1/o2)
    1/0.07587 = (1/7.4) - (1/16.875)
    i2 = 13.179

    Thank you both :smile:
     
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