3. Diatomic line. Consider a line of atoms ABAB.....AB, with A-B bond length of a/2. The form factors are fa and f for atoms A, B, respectively. The incident beam of x- rays is perpendicular to the line of atoms. (a) Show that the interference condition is nλ = a cose, where is the angle between the diffraction beam and the line of atoms. (b) Show that the intensity of the diffracted beam is proportional to A A f₁-f² for n odd, and to \ƒÃ +ƒÂ for n even. (c) Explain what happens if fA=fB.

3. Diatomic line. Consider a line of atoms ABAB.....AB, with A-B bond length of a/2. The form factors are fa and f for atoms A, B, respectively. The incident beam of x- rays is perpendicular to the line of atoms. (a) Show that the interference condition is nλ = a cose, where is the angle between the diffraction beam and the line of atoms. (b) Show that the intensity of the diffracted beam is proportional to A A f₁-f² for n odd, and to \ƒÃ +ƒÂ for n even. (c) Explain what happens if fA=fB.