Diffraction from a linear array and a square array the diffraction pattern of a linear structure of

Question:

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) A flat photographic plate is placed behind the fiber and normal to the incident beam. Sketch roughly the appearance of the diffraction pattern on the plate.?

(c) A single plane of atoms forms a square lattice of lattice constant a. The plane is normal to the incident x-ray beam. Sketch roughly the appearance of the diffraction pattern on the photographic plate. The diffraction from a plane of atoms can be inferred from the patterns for two perpendicular lines of atoms.?

(d) Figure 20 shows the electron diffraction pattern in the backward direction from the nickel atoms on the (110) surface of a nickel crystal. Explain the orientation of the diffraction pattern in relation to the atomic positions of the surface atoms shown in the model. Assume that only the surface atoms are effective in the reflection of low-energy electrons.?