In the Stern Gerlach experiment the Ag beam is split in two beams of half intensity of the original beam due to the equal distribution of spin up and spin down electrons. Considering that each of the split beams is composed of only one type of electrons (let's say spin up), if we pass this beam through a second Stern Gerlach apparatus at some relative angle from the first one I would expect to see only one beam. Either up or down depending on the relative angle between the second apparatus to the first one. Nevertheless, I read that an experiment like this will produce actually two other beam of different intensity depending on the angle. Why is this so?