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NEET Sample Paper NEET Sample Test Paper-53

  • question_answer
    In a double-slit experiment, two parallel slits are illuminated first by light of wavelength 400 nm and then by light of unknown wavelength. The fourth-order dark fringe resulting from the known wavelength of light falls in the same place on the screen as the second-order bright fringe from the unknown wavelength. The value of unknown wavelength of the light is-

    A) 900 nm            

    B) 700 nm

    C) 300 nm            

    D) none of these

    Correct Answer: B

    Solution :

    \[\frac{(2n-1){{\lambda }_{1}}D}{2D}\,\,=\,\,\frac{m{{\lambda }_{2}}D}{d}\] \[\frac{(2n-1)400}{2}\,\,=\,\,2{{\lambda }_{2}}\] \[{{\lambda }_{2}}\,\,=\,\,\frac{7}{4}\,\,\times 400\,\,=\,\,700\,nm\]


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