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NEET NEET SOLVED PAPER 2018

  • question_answer
    In Young's double slit experiment the separation d between the slits is 2 mm, the wavelength \[\lambda \] of the light used is \[\text{5896}\overset{o}{\mathop{\text{A}}}\,\] and distance D between the screen and slits is 100 cm. It is found that the angular width of the fringes is\[\text{0}\text{.20 }\!\!{}^\circ\!\!\text{ }\]. To increase the fringe angular width to \[\text{0}\text{.21 }\!\!{}^\circ\!\!\text{ }\] (with same \[\lambda \] and D) the separation between the slits needs to be changed to [NEET - 2018]

    A)  2.1 mm                      

    B)  1.9 mm

    C)  1.8 mm                      

    D)  1.7 mm

    Correct Answer: B

    Solution :

    Angular width \[=\frac{\lambda }{d}\] \[0.20{}^\circ =\frac{\lambda }{2mm}\]                 ?(i) \[0.21{}^\circ =\frac{\lambda }{d}\]                        ?(ii) Dividing we get, \[\frac{0.20}{0.21}=\frac{d}{2mm}\] \[\therefore d=1.9mm\]


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