In problems related to Interference and Diffraction fringes - I often have encountered phrases like "bright fringes 1.5 mm apart" or "distance between first bright fringe and 4th dark fringe". Fringe is some sort of rectangle not a point. we can talk about distance between two points not distance between two say, bands.
I think both interference and diffraction fringes are equal width - determined by wavelength, distance between slits and screen and distance between slits or width of one slit.
in one text book - it is mentioned that in diffraction fringe widths are not same where it is same in interference. Is it right?