 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/2017/s3/1/b/solution

The emitted photon has energy

E_{3} - E_{2} = Ry (1/4 - 1/9) = 5 Ry /36

. Therefore

λ = \frac{36 h c}{5 Ry} ≃ 656 nm .

This is the Balmer-alpha transition in this approximation. Absorption in the reverse direction has the same photon energy; fine structure and radiative corrections are beyond the model.

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