Double-slit experiment. (a) Suppose you illuminate the slits with 589 nm yellow sodium light and observe a 4.5 cm bright-fringe spacing on a screen 1.75 m away. What's the slit spacing? (b) A double-slit system with slit separation 0.340 mm is used to determine the wavelength of light passed by a filter. The resulting bright fringes are 2.58 mm apart on a screen 1.5 m away. What's the wavelength?