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Homework Help: A lens and a convex mirror problem

  1. Jun 25, 2011 #1
    1. The problem statement, all variables and given/known data
    A body is positioned 40 cm from the left of a lens (f=30) and the lens is positioned 100cm left of a convex mirror (|R|=60), where will be the image and what type and magnitude will it have?

    2. Relevant equations
    1/u + 1/v = 1/f

    3. The attempt at a solution
    I tried to calculate the image after the lens - and got v = 120 cm.

    Now, I don't know how to interpret the answer.
    Can anyone help me out on this?


    Attached Files:

  2. jcsd
  3. Jun 25, 2011 #2


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    Homework Helper

    The convex mirror interrupt the rays to form the real image.
    So (120 - 100) = 20 cm becomes the virtual object distance for the convex mirror. Now proceed.
  4. Jun 25, 2011 #3
    That's my problem, now it is considered concave?
  5. Jun 25, 2011 #4


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    Homework Helper

    You can consider the mirror concave, and find the image distance that way, or you take it convex and use negative object distance.

    Last edited: Jun 25, 2011
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