On introducing a thin sheet if thickness 2 × 10^–6 m and refractive index 1.5 in the path of one of the waves, central bright maxima shifts by n fringes. Wavelength of the wave used is 5000 Å, then n is

2

$\text{Shift in number of fringes is given by } n\lambda = (\mu -1)t$

$ n = \frac{(\mu -1)t}{\lambda} = \frac{0.5\times 2\times 10^{-6}}{5\times 10^{-7}} = 2$