A double-slit apparatus is immersed in a liquid of refractive index 1.33. It has slit separation of 1 mm, and the distance between the plane of slits and the screen is 1.33 m. The slits are illuminated by a parallel beam of light whose wavelength in air is 6300A˚.
(i) Calculate the fringe-width.
(ii) One of the slits of the apparatus is covered by a thin glass sheet of refractive index 1.53. Find the smallest thickness of the sheet to bring the adjacent minimum on the axis.