In the YDSE, the monochromatic source of wavelength `lambda` is placed at a distance `d/2` from the central axis (as shown in the figure), where d is the separation between the two slits `S_1 and S_2` .
(a)Find the position of the central maxima.
(b) Find the order of interference formed at O.
(c)Now, S is placed on centre dotted line. Find the minimum thickness of the film of refractive indes `mu =1.5` to be placed in front of `S_2` so that intensity at O becomes `3/4`th of the maximum intensity.
(Take `lambda=6000Å, d = 6mm`.)
