As shown in the figure, in Young's double slit experiment, a thin plate of thickness $\mathrm{t}=10 \mid \mathrm{a} \cdot \mathrm{m}$ and refractive index $\mu=1.2$ is inserted infront of slit Si . The experiment is conducted in air $(\mu=$ and uses a monochromatic light of wavelength $\lambda=500 \mathrm{~nm}$. Due to the insertion of the plate, central maxima is shifted by a distance of xpo. po is the fringe-width before the insertion of th plate. The value of the $x$ is $\_\_\_\_$ .