A transparent slab of thickness t and refractive index $\mathrm{\mu }$ is inserted in front of upper slit of YDSE apparatus. The wavelength of light used is $\mathrm{\lambda }$. Assume that there is no absorption of light by the slab. Mark the correct statement(s).

The intensity of dark fringes will be 0, if slits are identical.

The change in optical path due to insertion of plate is $\mathrm{\mu t}$.

The change in optical path due to insertion of plate is $(\mathrm{\mu }-1)\mathrm{t}$.

For making intensity zero at center of screen, the thickness can be $\frac{5\mathrm{\lambda }}{2(\mathrm{\mu }-1)}$.