 Solution

ID: past-exam-of-the-physics-course-of-the-year-4-of-the-natural-sciences-course-of-the-university-of-cambridge/2016/paper-1/section-b/b1/a/solution

In the paper's convention

J

is measured in units of

ℏ

, and

g

is dimensionless. For

m = - J, - J + 1, \dots, J

μ_{z} = - g μ_{B} m, E_{m} = - μ_{z} B = g μ_{B} B m .

J

instead denotes dimensional angular momentum, its coefficient must contain

1/ℏ

. This resolves the units of the printed moment formula.

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