In a laboratory demonstration of interference, two slits 0.25mm apart are illuminated with monochromatic light of wavelength 650nm. The screen is fixed 1.6m away from the slits, but its lower edge cuts off the pattern below y=−15mm while the upper edge cuts off everything above y=+18mm (origin at the central bright).
(i) Calculate the total number of complete bright fringes that are actually visible on the screen.
(ii) Calculate the total number of complete dark fringes that are actually visible on the screen.
(iii) Identify whether the topmost visible bright fringe is incomplete, just complete, or followed by an incomplete fringe that has been cut off. Justify your answer with a short calculation.