Interference fringes are observed on a screen
by illuminating two thin slits 1 mm apart with a
light source ( = 632.8 nm). The distance
between the screen and the slits is 100 cm. If
a bright fringe is observed on a screen at a
distance of 1.27 mm from the central bright
fringe, then the path difference between the
waves, which are reaching this point from the
slits is close is