Wave Optics

One of the slits in Young's double slit experiment is covered with a transparent sheet of thickness \(2.9 \times 10^{-3} \mathrm{~cm}\). The central fringe shifts to a position originally occupied by the \(25^{\text {th }}\) bright fringe. If \(\lambda=5800\) \(\mathop A\limits^o\), the refractive index of the sheet is