Answer Happy

22. Choose all of the following statements that are true about the vector (S) in the spin space in the state x(t)): (I) The vector (S) can be thought to be precessing about the z axis at an angle 2a. (II) The vector (S) can be thought to be precessing about the z axis with a frequency w = Bo (III) All the three components of vector ($) change as it precesses about the z axis. (a) (I) and (II) only (b) (I) and (III) only (c) (II) and (III) only (d) (I), (II) and (III) 23. Choose a three dimensional coordinate system in the spin space with the z axis in the vertical di- rection. Draw a sketch showing the precession of ($) about the z axis when the state of the system starts out in a 1)2 + b ). Show the angle that (S) makes with the z axis and the precession frequency explicitly. Show the projection of ($) along the z, y and z axes at two separate times. Explain in words why the projection of ($) along the z direction does not change with time but those along the r and y directions change with time.