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Homework Help: Graphing conves lense relationships to find focal lenght with slope

  1. Nov 28, 2009 #1
    1. The problem statement, all variables and given/known data
    I need to find the relationship between object-lens distance and image-lens distance for a lense(converging) but cannot graph the relationship in a way that the focal lenght is the slope for the graph

    2. Relevant equations
    1/u + 1/v = 1/f
    where u= object lense distance and v= image lense distance and f= focal lenght

    y=mx+b --> I would like m=focal lenght and b=0

    3. The attempt at a solution
    so far, I can only come up with:
    -u ( 1/[uv]) = -1/v
    thus ( 1/[uv]) is the slope.. but f= (v+u)/(uv)
  2. jcsd
  3. Nov 29, 2009 #2


    User Avatar
    Homework Helper

    You can write the lens equation as
    (1/u)/(1/f) + (1/v)/(1/f) = 1.
    It is in the form of
    x/a + y/b = 1.

    Draw the graph 1/u vs 1/v. You will get a straight line with slope (-1). The intercept on x and y-axis are equal and it is equal to 1/f.
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