A double slit setup is shown in the figure. One of the slits is in medium 2 of refractive index $\mathrm{n}_2$. The other slit is at the interface of this medium with another medium 1 of refractive index $\mathrm{n}_1\left(\neq \mathrm{n}_2\right)$. The line joining the slits is perpendicular to the interface and the distance between the slits is d . The slit widths are much smaller than d . A monochromatic parallel beam of light is incident on the slits from medium 1. A detector is placed in medium 2 at a large distance from the slits, and at an angle $\theta$ from the line joining them, so that $\theta$ equals the angle of refraction of the beam. Consider two approximately parallel rays from the slits received by the detector.