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24 August, 01:50

What is the object distance? you will need to use the magnification equation to find a relationship between s and s′. then substitute into the thin lens equation to solve for s.?

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  1. 24 August, 03:31
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    For lens in S I system, 1/v - 1 / u = 1/f

    gives 1/v=1/f + 1/u,

    multiply by 'u' on both sides

    u/v = u/f + 1

    u/v = (u+f) / f

    inverting,

    v/u = f / (u+f)

    Therefore magnification 'm' = v/u=f / (u+f)

    'm' = f / (u+f)

    Given magnification is 5 / 9

    f / (u+f) = 5 / 9

    object distance 'u' = 4f / 5

    Now substitute for focal length f (focal length of diverging lens is negative)
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