A young’s double slit system was erected in a tank and a sodium lamp with a narrow slit is situated outside Interference fringes are produced on the opposite side. Now we fill up the tank using a substance that changes the fringe separation by thirty five percent. Explain the reason behind it and also discuss the change in separation. Calculate the refractive index of the substance.

A young’s double slit system was erected in a tank and a sodium lamp with a narrow slit is situated outside Interference fringes are produced on the opposite side. Now we fill up the tank using a substance that changes the fringe separation by thirty five percent. Explain the reason behind it and also discuss the change in separation. Calculate the refractive index of the substance.