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Refraction Formula For Thin Lens

  1. Nov 9, 2015 #1
    I was browsing about my optics books,completing numericals and stuff
    When I found a a statement called different lens formulas
    It had 2 formulas
    One,called the thin lens formula or rather the geometric sign convention formula was called 1/v-1/u=1/f(Symbols have their usual meanings) and another one called the virtual-real sign convention formula which was 1/v+1/u=1/f
    I know that for a thin lens 1/S0 +1/SI=1/F
    Where S0,SI are the object and image distances respectively
    So is the statement correct
    Or is it just one formula made into two because of the Cartesian SIgn Convention???
    Some insight is much appreciated
  2. jcsd
  3. Nov 9, 2015 #2


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    Both are 'correct'. See Hyperphysics where they tell you all the details.

    And yes, the Cartesian sign convention flips the sign.

    (But now I am personally confused by the minus sign for f in the second link :frown: . Anyone ? )

    perhaps this helps ?
    Last edited: Nov 9, 2015
  4. Nov 9, 2015 #3
    It helped quite a lot
    But my question is why are there 2 lens equations to begin with
    I personally use the gaussian formula with sign convention
    I never really have used the real-virtual one
  5. Nov 10, 2015 #4


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    Same here. But the link reveals that
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