 Solution

ID: past-exam-of-the-short-options-paper-shared-by-prelims-and-parts-a-and-b-of-the-physics-course-of-the-university-of-oxford/2016/s3/3/5/a/solution

The Lyman-alpha gap is

3 Z^{2} (μ / m_{e}) Ry /4

λ = 4 h c / [3 Z^{2} (μ / m_{e}) Ry]

. For heavy lithium nucleus and

Z = 3

λ ≃ 13.5 nm

. A specified lithium isotope would permit the small reduced-mass correction; no isotope is supplied.

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