Consider a periodic array of slits with a period of A through which light propagates. Let O be the angle of incidence. Show that diffraction occurs at angles O' that satisfy the following equation: A sin 0 + A sinO' = ma, m = 1,2,3,... (b) Let z be the direction of periodicity. Show that the equation above can also be written as k, - k, = m(2n/A), m = 1,2,3