L. mention two differences between optical and acoustic branch. . show that the situ ation of vibration of monoatomic linear lattice at qux i.e., zone boundary)

L. Mention two differences between Optical and Acoustic branch. . Show that the situ ation of vibration of monoatomic linear lattice at qux i.e., zone boundary) is equivalent to Bragg Reflection of X-rays. Discuss the origin of Diamagnetism.