Interference pattern with Young's double slits 1.5 mm apart are formed on a screen at a distance 1.5 m from the plane of slits. In the path of the beam of one of the slits, a transparent film of 10 micron thickness and of refractive index 1.6 is interposed while in the path of the beam from the other slit a transparent film of 15 micron thickness and of refractive index 1.2 is interposed. Find the displacement of the fringe pattern.