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Homework Help: Optics Thin Lens Equation

  1. Jan 18, 2008 #1
    kk so i found out the steps involved deriving the thin lens equation, but what i dont get is when you have 2 similar triangles say triangle abd,edf are congruent how does the 2 triangles make it so its di/f-1. so what im basically asking is can someone thourougly explain to me whats going on in the steps to deriving the thin lens equation thnx.
  2. jcsd
  3. Jan 18, 2008 #2


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    Homework Helper

    Remember: the thin lens equations are only approximation to the real world. one way to get these formulas is to study refraction at spherical surfaces using Fermat's principle and small angle approximation, amongst other things. It is not a straight forward derviation. See for example: "Optics" by Hecht
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