The figure shows a Young's double slit experimental setup. It is observed that when a thin transparent sheet of thickness t and refractive index $$\mu$$ is put in front of one of the slits, the central maximum gets shifted by a distance equal to n fringe width. If the wavelength of light used is $$\lambda$$ then t will be:

A

$$\frac{D\lambda}{a(\mu - 1)}$$

B

$$\frac{n\lambda}{(\mu - 1)}$$

C

$$\frac{2n\lambda}{(\mu - 1)}$$

D

$$\frac{2D\lambda}{a(\mu - 1)}$$