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J & K CET Engineering J and K - CET Engineering Solved Paper-2009

  • question_answer
    In Young's double slit experiment, the fringe width with light of wavelength \[6000\text{ }\overset{\text{o}}{\mathop{\text{A}}}\,\]is\[3\text{ }mm\]. The fringe width, when the wavelength of light is changed to \[4000\text{ }\overset{\text{o}}{\mathop{\text{A}}}\,\]is

    A)   \[3\text{ }mm\]

    B)   \[1\text{ }mm\]

    C)  \[\text{2 }mm\]

    D)  \[\text{4 }mm\]

    Correct Answer: C

    Solution :

    Fringe width, \[\beta =\frac{\lambda D}{d}\] \[\frac{\beta }{\lambda }=\frac{D}{d}\]= constant for an experiment \[\therefore \] \[\frac{\beta }{\lambda }=\frac{\beta '}{\lambda '}\] \[\Rightarrow \] \[\frac{3}{6000}=\frac{\beta '}{4000}\] \[\Rightarrow \] \[\beta '=2mm\]


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