Question

Effect of thin transparent plate in the path of one of the interfering beam.in young's double slit experiment. Have anyone caliber to derivate it?

Answer 1

thin transparent plate causes a path difference equivalent to
(n-1)d
where n is the refractive index of the plate
and d is its thickness
it is explained by the concept of equivalent
distance
in air, the distance covered is d,
then in some medium with refractive index n,equivalent distance covered is nd but delete that d distance covered in air so equivalent distance is (n-1)d which is the path difference between the two waves