1. The problem statement, all variables and given/known data A single slit of width 1.50 * 10-6m is illuminated with light of wavelength 500.0 nm. Find the angular width of the central maximum. 2. Relevant equations θ = λ / b 3. The attempt at a solution b = 1.50 * 10-6m λ = 5.000 * 10-7 θ = λ / b = 0.333 = 19.1° But the answer is 38.9°. All my calculation of diffraction on single slit is off-target. It seems there is a fundamental point that I am missing. Please help.