A plate of thickness t made of a material of refractive index μ is placed in front of one of the slits in a double slit experiment. (a) Find the change iii the optical path due to introduction of the plate. (b) What should be the minimum thickness t which will make the intensity at the center of the fringe pattern aero? Wavelength of the light used is λ . Neglect any absorption of light in the plate.

Question

Philoid · Accepted Answer

(a)The optical path length in vacuum is and that introduce due to the plate is .

Hence, the change in optical path length is .

(b) For the central maximum to be zero, the two incoming waves should be completely out of phase. Hence the change in optical path difference should be equal to .