Question

A plate of thickness t made of material of refractive index $\mu$ is placed in front of one of the slits in a double slit experiment. What would be the minimum thickness t which will make the intensity at the center of the fringe pattern zero?

Answer 1

 Change in the optical path = μt – t = (μ – 1)t

To have a dark fringe at the centre the pattern should shift by one half of a fringe. ⇒ (μ – 1)t = λ/2 ⇒

 t = λ/2(μ – 1)