During a project, a learner records the interference pattern produced by two slits 0.35mm apart on a CCD sensor placed 1.80m away. The sensor manufacturer states that each pixel is a square of side 4.0μm. On examining the image, the learner finds that the centres of the first and the twenty-first bright fringes differ by 1760 pixels along the vertical direction.
(i) Convert this pixel separation into an actual distance on the screen.
(ii) From these data, calculate the wavelength of the laser used, quoting the answer to an appropriate number of significant figures.
(iii) If the uncertainty in locating each fringe centre is ±2 pixels, estimate the percentage uncertainty in the value of the wavelength.