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Homework Help: A convex spherical mirror

  1. Mar 9, 2010 #1
    1. The problem statement, all variables and given/known data

    A convex spherical mirror has a radius of curvature R = 20.0 cm and produces an
    upright image precisely one-quarter the size of an object. Calculate the
    separation distance between the object and its image?

    2. Relevant equations

    M = (image height)/(object height) = h'/h = -q/p

    1/q + 1/p = 1/f

    q = length from mirror to image
    p = length from mirroe to object
    f = focal point

    3. The attempt at a solution

    FOR FINDING p (length from mirror to object)

    h = 4h'

    h'/h = -q/p

    h'/4h' = -q/p

    q = -p/4

    1/(-q) = 1/f - 1/p

    4/p + 1/p = 1/f

    5/P = 1/10

    P = 50

    I know this cannot be right because when i go to calculate q it is greater than the focal point and that does not work.
    Any help would be great.
  2. jcsd
  3. Mar 9, 2010 #2


    User Avatar
    Homework Helper

    4/p + 1/p = 1/f
    This substitution is not correct.
    Use proper sign conversion for image distance, object distance and the focal length.
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