A double-slit experiment is set up using helium-neon laser ( = 633 nm). Then a very thin film of glass (n = 1.50) is placed over one of the slits.

A double-slit experiment is set up using helium-neon laser (λ = 633 nm). Then a very thin film of glass (n = 1.50) is placed over one of the slits. Afterward, the central point on the screen is occupied by what had been the m = 10 dark fringe. How thick is them glass?