1. The problem statement, all variables and given/known data I have a few questions because of the fact I just don't understand any of this....... 1.A helium-neon laser (l=656 nm) illuminates a single slit and is observed on a screen 1.9 m behind the slit. The distance between the first and second minima in the diffraction pattern is 5.45 mm. What is the width (in mm) of the slit? w=2*(wavelength)*L/a wavelength= 656 x 10^-9 m L=1.9 m a=5.45 x 10^-3 m 3. The attempt at a solution I plugged and chugged and got 4.574 x 10^-4.....what did i do wrong?