In a young’s double slit experiment the distance between slits S1 and S2 is d and distance of slit plane from the screen is `D (gtgt d)`. The point source of light (S) is placed a distance ` (d) / (2 )` below the principal axis in the focal plane of the convex lens (L). The slits S1 and S2 are located symmetrically with respect to the principal axis of the lens. Focal length of the lens is `f (gtgt d)`.
Find the distance of the central maxima of the fringe pattern from the centre (O) of the screen.

Answer

`(Dd)/(2f)`