Atom and its reaction while travelling in a magnetic field

[radioactive8]

Hello
I was reading a book about quantum mechanics and in some point it used as an example the reaction of the atom while its traveling through a magnetic field . So the author described an atom as a magnetic arrow ( which isn't complety right but he did that so he can reveal the truth afterwards and so we readers end up in a mathetical dead end in an experiment using a stern-gerlach analyser .. so he said That if we have a dissimilar magnetic field for example which its trend going up he said that according to the trend of the atom's arrow it will even travel up by μ_β or down by μ_β . So hear is my question : how can it have the same declination ?
2

 

[DrClaude]

So hear is my question : how can it have the same declination ?
2

By declination I imagine you mean the angle of the trajectory after the magnetic field with respect to the original direction of propagation. In that case, it is set by the strength of the magnetic field and the magnetic moment of the atom, which I imagine is here a hyrogen atom, which can take only two discrete values which are exactly opposite. This is the "quantum" in quantum mechanics: the magnetic moment is quantized and can only take a discrete set of values.

 

[jtbell]

More precisely, the magnitude of the magnetic moment is fixed, but its orientation can take on a discrete set of values (two in this case).