113 B spin up beam down n -spin Z Z Figure 1: The Stern-Gerlach experiment (d) Suppose we start with N particles. We first pass them through a magnetic field in the z-direction, and block the beam that goes down. After this process, you find that only particles remain. They then go through a magnetic field in the x-z plane, an angle from the z-axis, and the beam that goes against the direction of the field is blocked. Then you have a magnetic field in the z-direction again, and block the beam that goes up this time. How many particles come out? Compare with the case without the middle magnetic field