CBSE NOTES CLASS 12 PHYSICS
CHAPTER 10 WAVE OPTICS
Dark and bright fringes are equally spaced and the distance between two consecutive bright fringes or two consecutive dark fringes is given by
The central point O will be bright because S1O = S2O and it will correspond to n = 0. If we consider the line perpendicular to the plane of the paper and passing through O [i.e., along the y-axis] then all points on this line will be equidistant from S1 and S2 and we will have a bright central fringe which is a straight line.
All other fringes will be hyperbolas. If D >> β then they will be almost straight lines.