518 Atomic PhysicsQ42.25(a)The terms “I define” and “this part of the universe” seem vague, in contrast to the precisionof the rest of the statement. But the statement is true in the sense of being experimentallyverifiable. The way to test the orientation of the magnetic moment of an electron is to applya magnetic field to it. When that is done for any electron, it has precisely a 50% chance ofbeing either spin-up or spin-down. Its spin magnetic moment vector must make one of twoallowed angles with the applied magnetic field. They are given by cosθ==SSz1232andcos=−. You can calculate as many digits of the two angles allowed by “spacequantization” as you wish.(b)This statement may be true. There is no reason to suppose that an ant can comprehend thecosmos, and no reason to suppose that a human can comprehend all of it. Our experiencewith macroscopic objects does not prepare us to understand quantum particles. On theother hand, what seems strange to us now may be the common knowledge of tomorrow.
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Magnetic Field, Balmer series, Spin magnetic moment, Paschen series