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Homework Help: How to use a Spherometer

  1. Oct 28, 2006 #1
    I'm trying to figure out what/how to use one without seeing/having one.

    Am I right in saying the following.

    It has three legs, which form the vertices of an equilateral triangle. The centre leg is placed onto a lens, and it's adjusted until they all balance/evne out. Then the distance of it has been adjusted is noted, and put into this formula (on wikipedia I found);

    r = [ (a^2 + 3h^2)/6h ]

    in which a = distance between feet, and h is the distance it's been adjusted.

    Is there a diagrammatical representation of this? Can someone correct any mistakes?

  2. jcsd
  3. Oct 28, 2006 #2


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    Science Advisor
    Homework Helper

    There are three fixed legs separated by distance a and an adjustable leg in the center of the triangle.


    The flat disk is engraved with the markings to show the d value. The vertical flat is aligned with the markings to read d.
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