An unpolarised beam of intensity $$2 a^2$$ passes through a thin polaroid. Assuming zero absorption in the polaroid, the intensity of emergent plane polarised light is

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.

An interference pattern is observed by Young’s double slit experiment. If now the separation between coherent source is halved and the distance of screen from coherent sources