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Convex mirrors

  1. Mar 24, 2007 #1
    1. The radius of Earth is 6.40 x 10³ km. The moon is about 3.84 x 10^5 km away from Earth and has a diameter of 3475 km. The Pacific Ocean surface, which can be considered a convex mirror, forms a virtual image of the moon. What is the diameter of that image?

    Code (Text):
    2. 1/p + 1/q = 1/f
    Code (Text):
    M = h'/h = -q/p

    3. Ok. So since the image is virtual, q (image distance) is negative. p (object distance) is 3.84 x 10^5 km and h(object height) is 3475 m. Could the radius of Earth be used as the radius of curvature? I'm confused as to how to set up the equations in order to get the diameter of the image(h')
  2. jcsd
  3. Mar 24, 2007 #2


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    Homework Helper
    Gold Member

    Yes, use the radius of the earth as the radius of the mirror formed by the pacific ocean. Think of the water covered part of the earth as a giant, convex, spherical mirror.

    HINT: Can you find the focal length of the ocean from what you know?
    Last edited: Mar 24, 2007
  4. Mar 25, 2007 #3
    Ok. yeah that clears stuff up cuz I can get focal length from the radius. Thanks.
  5. Mar 25, 2007 #4
    I'm getting like 28.7 km for an answer. Can anyone confirm?
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