The maximum number of interference maxima for slit separation equal to two times the wavelength in YDSE, is.

To demonstrate interference we require two sources which emit radiations of

On introducing a thin film in the path of one of the two interfering beams, the central fringe will shift by one fringe width. If $\mu =1.5$, the thickness of the film is (wavelength of monochromatic light is $\lambda$ )