A diffraction pattern is produced on a screen 140 cm from a single slit using monochromatic light of wavelength 500 nm. The distance from the center of the central maximum to the first order maximum is 3 mm. Calculate the slit width (assume first order maximum is halfway between the first and second order minima). So things we know- From the slit to the screen is 140 cm Wavelength = 500 nm from the center of the central maximum to the first order is 3 mm. if we use: Sin of the angle = (M * Wavelength)/d = sin of the angle = (1 * 500x10^-7) / .003 That gives the angle of the central maximum which we can then plug into sin angle=wavelength/slit width?