2. Sample Papers
  3. JEE Main & Advanced

JEE Main & Advanced Sample Paper JEE Main - Mock Test - 18

  • question_answer
    When one of the slits of Youngs experiment is covered with a transparent sheet of thickness 4.8 mm, the central fringe shifts to a position originally occupied by the 30th bright fringe. What should be the thickness of the sheet if the central fringe has to shift to the position occupied by 20th bright fringe?

    A) 3.8 mm

    B)          1.6 mm

    C) 7.6 mm         

    D) 3.2 mm

    Correct Answer: D

    Solution :

    [d] \[\Delta x=\frac{D(\mu -1)t}{d}.\]Also \[\Delta x=\frac{nD\lambda }{d}.\] \[\therefore \]\[\frac{D(\mu -1)t}{d}=\frac{nD\lambda }{d}\]or\[(\mu -1)t=n\lambda \] or\[\frac{{{t}_{1}}}{{{t}_{2}}}=\frac{{{t}_{1}}}{{{t}_{2}}}\Rightarrow {{t}_{2}}=\frac{{{n}_{2}}{{t}_{1}}}{{{n}_{1}}}\]or\[{{t}_{2}}=\frac{20\times 4.8}{30}=3.2mm.\]


You need to login to perform this action.
You will be redirected in 3 sec spinner