In the narrow double-slit interference experiment, the two slits are 2mm apart, the distance from the screen to the double-slit mask is 1m. The distance between the 2 10th bright fringes in the 2 central bright fringes is 4.5 mm. a) Determine the wavelength of light used.b) Change the monochromatic light source to natural light (400-700nm). Please describe the observed phenomenon on the screen. At a point 1mm away from the central bright fringe, a narrow slit of a spectrometer with 2 source slits is placed. Let's determine the number of bright spots on the universal camera screen