In a Young's double slit experiment, let A and B be the two slits. A thin film of thickness t and refractive index is placed in front of A. Let
fringe width the central maximum will shift
towards A
towards B
Let distance between the slits,
wavelength of light,
distance from the slits to the screen.
For a point P on the screen at a distance x from the centre of the screen, path difference
Path difference introduced due to film .
For central maximum at