JCECE Engineering JCECE Engineering Solved Paper-2007

  • question_answer
    Interference was observed in an interference chamber when air was present. Now, the chamber is evacuated and if the same light is used, a careful observation will show

    A)  no interference

    B)   interference with bright band

    C)   interference with dark bands

    D)  interference in which breadth of the fringe will be slightly increased

    Correct Answer: D

    Solution :

    When chamber is evacuated, the refractive index \[(\mu )\] decreases. Therefore, wavelength \[\left( \lambda \propto \frac{1}{\mu } \right)\]increases. Now, fringe width is given by                 \[\beta =\frac{\lambda D}{d}\] \[\Rightarrow \]               \[\beta \propto \lambda \] Therefore, as wavelength increases, the fringe width will increase.


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