In Young’s double slit experiment a monochromatic light of wavelength` lambda` from a distant point source is inci- dent upon the two identical slits.The interference pattern is viewed on a distant screen. Intensity at a point P is equal to the intensity due to individual slits (equal to` I_(0)`). A thin piece of glass of thickness t and refractive index `mu` is placed in front of the slit which is at larger distance from point P, perpendicular to the light path. Assume no absorption of light energy by the glass.
(a) Write intensity at point P as a function of t.
(b) Write all values of t for which the intensity at P is minimum.

Answer

(a)`4I_(0)cos^(2)((pi)/(3)+(pi)/(lambda)(mu-1)t)`
(b)`t=((2n-1)lambda)/(2(mu-1))-(lambda)/(3(mu-1))"wheren=1,2,3...`