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Homework Help: Light reflections in concave/convex mirrors

  1. Feb 25, 2009 #1
    1. The problem statement, all variables and given/known data

    A man polishes the insided and outside of a hubcap that is a section of a sphere. When he looks into one side of the hubcap, he sees an image of his face 30cm behind the hubcap. He then turns the hubcap over and sees another image of his face 10 cm behind the hubcap.
    a)How far is his face from the hubcap?
    b)What is the radius of curvature of the hubcap?
    c)What is the magnification for each image?
    d)Are the images real or virtual?
    e)Are the images upright or inverted?

    2. Relevant equations

    1/Di + 1/Do = 1/f Di= distance of image Do=distance of object f= focal point

    M= Hi/Ho = -Di/Do M= magnification Hi= height of image Ho= height of object

    3. The attempt at a solution

    a) i believe you have to use the first equation but i am unsure of how to use the given data in it, could you possibly do..... 1/-30 + 1/-10 + 2/Di = 2/f ???

    b)find the focal point and double it i believe

    c)use M= -Di/Do for both but i dont know the Do from part "a"

    d)virtual because the image is behind the mirror

    e)upright because all virtual images are upright?

    -- i think i am on the right track, but not sure--
  2. jcsd
  3. Feb 26, 2009 #2


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    Homework Helper

    Keeping Do same, write two equation for two cases. Since R is the same fore both the case, f is the same, but sign will change. From these equation you can find Do. Once you find Do, other thing are easy.
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