Question

why only one component of angular momentum is quantized
??​

Answer 1

Because Angular Momentum is one of the vector components of the 3D quantity called Activity, whose scalar part is Mechanical Action (a la Maupertuis). Since interactions are the quantized exchange of activity then both action is quantized (as Planck was compelled to admit) but so is angular momentum, as Bohr found

Answer 2

Explanation:

Because Angular Momentum is one of the vector components of the 3D quantity called Activity, whose scalar part is Mechanical Action (a la Maupertuis). Since interactions are the quantized exchange of activity then both action is quantized (as Planck was compelled to admit) but so is angular momentum, as Bohr found.