question_answer

When a thin transparent film is Placed just in front of one of the slits in the Young's double  slit experiment using white light, what change results in the  fringe system?   

Answer:

                          If\[\mu \] is-the refractive index and t the thickness of the thin film, then the entire interference pattern gets displaced by distance, \[\Delta x=\frac{D}{d}(\mu -1)t\] As \[\mu \] depends on \[\lambda \] (increases with decreasing \[\lambda \]), the violet fringe is shifted farther than the red fringe. So there is a kind of dispersion in the central white fringe.