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    The inverse law states that the intensity of illumination is inversely proportional to the square of the distance from the point source.

    I  _1_
    d2

    A student carried out an investigation, measuring a set of intensity readings ( I ) on a light meter at various distances ( d) from a point source of light. The results are shown in the table below :

    Intensity ( I ) W/m2 15 48 116 249 442 761
    distance ( d ) cm 114 64 41 28 21 16
    1/distance2 ( 1/d2 ) cm-2
    1/distance2 ( 1/d2 ) cm-2 X10-5

    9a) Plot a graph of intensity ( y-axis ) against distance ( x-axis ).What
    does this graph indicate ?

    9.b) Plot another graph of intensity (y-axis) against 1/ d2 (x-axis)


    9c) Using the results , develop a relationship between ( I ) and ( d )
    and hence prove that the inverse law holds. Remember I x d2 = Constant

    9 d) Find the gradient of the graph in (b).

    9e) Find the gradient of the graph in a) when d = 45 cm by drawing a tangent to the line and drawing a tangent to the line.
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    (Original post by mark000)
    The inverse law states that the intensity of illumination is inversely proportional to the square of the distance from the point source.

    I  _1_
    d2

    A student carried out an investigation, measuring a set of intensity readings ( I ) on a light meter at various distances ( d) from a point source of light. The results are shown in the table below :

    Intensity ( I ) W/m2 15 48 116 249 442 761
    distance ( d ) cm 114 64 41 28 21 16
    1/distance2 ( 1/d2 ) cm-2
    1/distance2 ( 1/d2 ) cm-2 X10-5

    9a) Plot a graph of intensity ( y-axis ) against distance ( x-axis ).What
    does this graph indicate ?

    9.b) Plot another graph of intensity (y-axis) against 1/ d2 (x-axis)


    9c) Using the results , develop a relationship between ( I ) and ( d )
    and hence prove that the inverse law holds. Remember I x d2 = Constant

    9 d) Find the gradient of the graph in (b).

    9e) Find the gradient of the graph in a) when d = 45 cm by drawing a tangent to the line and drawing a tangent to the line.
    What have you tried? What is your actual question?
 
 
 
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