Red light of wavelength 5400 $$\mathop A\limits^o $$ from a distant source falls on a slit 0.80 mm wide. Calculate the distance between first two dark bands on each side of central bright band in the diffraction pattern observed on a screen place 1.4 m from the slit.

Assertion : If a glass slab is placed in front of one of the slits, then fringe with will decrease.

Reason : Glass slab will produce an additional path difference.