1. Diffraction from a linear array and a square array. The diffraction pattern of a linear structure of lattice constant a is explained* in Fig. 19. Somewhat similar structures are important in molecular biology: DNA and many proteins are linear helices. (a) A cylindrical film is exposed to the diffraction pattern of Fig. 19b; the axis of the cylinder is coincident with the axis of the linear structure or fiber. Describe the appearance of the diffraction pattern on the film. (b)