Missing Order Condition in Grating Diffraction

Formula: k = (d)/(a) k', k' = ± 1, ± 2, ± 3, where 'k' is the order of the grating principal maximum, and 'k'' is the order of the single - slit diffraction minimum. Applicable Conditions: Parallel light incident normally on a diffraction grating. Explanation: When a direction simultaneously satisfies the conditions for a grating principal maximum and a single - slit diffraction minimum, that order of the principal maximum will be absent, known as a missing order. 'd' is the grating constant, 'a' is the single - slit width.