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Homework Help: Lenses and Optical Instruments

  1. Apr 26, 2009 #1
    A diverging lens with a focal length of -14 cm is placed 12 cm to the right of a converging lens with a focal length of 18 cm. An object is placed 33cm to the left of the converging lens.

    Where will the final image be located.

    1/f = 1/di + 1/do
    dob = L - dia

    After solve for the converging lens (a), the dia was 39.6cm. Then, to get the object distance from the diverging lens(b), the length between was subtracted from the image distance from (a). dob = 12-39.6 = -27.6

    I then solve for the object distance for the diverging lens and get a negative value. -28.4cm.
    It this correct? If so, is it simply just 28.4 cm BEHIND the diverging lens?
  2. jcsd
  3. Apr 26, 2009 #2


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    Staff Emeritus
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    Looks right. The negative number indicates a virtual image, i.e. it is to the left of the diverging lens.
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