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Radius of curvature using spherometer

  1. Jan 23, 2015 #1

    leojun

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    which formula is correct? spherometer.jpg or b55a8e505eea5106a0ee5bdbc5daa016.png
     
    leojun, Jan 23, 2015
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  3. Jan 23, 2015 #2

    A.T.

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    The one of the picture looks correctly derived. Where does the other one come from, and what is "a"?
     
    A.T., Jan 23, 2015
  4. Jan 23, 2015 #3

    leojun

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    We use second formula instead of the first formula to find the radius of curvature using spherometer.
    "a" in the second formula is the same as "b" in the first formula.
    The first formula is correct but i don't get why we use second formula instead of first.
    The two formula's are supposed to be the same r=R,but why are they different?
     
    leojun, Jan 23, 2015
  5. Jan 23, 2015 #4

    A.T.

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    I see no "b" in the first formula.
     
    A.T., Jan 23, 2015
  6. Jan 23, 2015 #5

    leojun

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    SORRY,"a" in the second formula is the same as "d" in the first formula
     
    leojun, Jan 23, 2015
  7. Jan 23, 2015 #6

    Bystander

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    "a" is the side length of the triangle, or distance between two of the three points.
     
    Bystander, Jan 23, 2015
  8. Jan 23, 2015 #7

    A.T.

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    I don't think so. I think Bystander is right and the formulas are equivalent.
     
    A.T., Jan 23, 2015
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