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Homework Help: Finding di and hi

  1. Jul 9, 2014 #1
    1. The problem statement, all variables and given/known data
    Lawn spheres placed on pedestals are convex mirrors. One such sphere has a diameter of 40.cm. A 12 cm robin sits in a tree 1.5m from the sphere. Make a representative sketch. Where is the image of the robin? How long is the robins image?

    2. Relevant equations

    3. The attempt at a solution
    I have a diagram but am stuck on where to go from here?
  2. jcsd
  3. Jul 9, 2014 #2


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    Homework Helper
    Gold Member

    Hello Capri,

    Welcome to Physics Forums! :smile:

    First, work your way to finding the focal length of the mirror.

    You know the diameter of the sphere. From that, you can determine the radius of curvature*. From there you should be able to look up some formula for the focal length as a function of the radius of curvature. Oh, and don't forget to pay attention to the +/- sign and how that relates to concave or convex mirrors.

    *[Edit: radius of curvature is often called center of curvature.]
    Last edited: Jul 9, 2014
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