In YDSE, D=1m, d=4mm and  $\lambda =\frac{1}{2}\text{mm}$ in the figure shown, a parallel beam of light is incident on the plane of the slits of YDSE. Light incident on the slit  $S_1$ passes through a medium of variable refractive index $\mu =(2x+1)$ (where x is the distance from the plane of slits in mm) up to a distance $\mathcal{l}=1\text{mm}$ before falling on $S_1$ rest of the space filled with air. Then choose the correct option(s):