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    A narrow beam of light is directed normally at a slit.
    a) blue filter placed in the path of a beam before it reaches the slit. distance across 5 fringes including the central fringe = 18mm find the width of the central fringe
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    (Original post by ashg99)
    A narrow beam of light is directed normally at a slit.
    a) blue filter placed in the path of a beam before it reaches the slit. distance across 5 fringes including the central fringe = 18mm find the width of the central fringe
    The central fringe is double the width of the other fringes, so we can take the total width of 5 fringes including the central fringe to be equal to 6 "outside fringes"

    18/6 = width of subsidiary fringes = 3mm

    because central fringe = 2xsubsidary fringes
    = 2*3 = 6mm

    If you then add 3+3+6+3+3 (the widths of all the fringes in order, the answer = 18mm, so central fringe = 6mm

    (I hope this makes sense, it did to me haha)
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    (Original post by jakepds)
    The central fringe is double the width of the other fringes, so we can take the total width of 5 fringes including the central fringe to be equal to 6 "outside fringes"

    18/6 = width of subsidiary fringes = 3mm

    because central fringe = 2xsubsidary fringes
    = 2*3 = 6mm

    If you then add 3+3+6+3+3 (the widths of all the fringes in order, the answer = 18mm, so central fringe = 6mm

    (I hope this makes sense, it did to me haha)
    Thanks mate it did make sense. LoL
 
 
 
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