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Atoms — Physics STD 12 Science — Question

Bihar BoardEnglish MediumSTD 12 SciencePhysicsAtoms5 Marks
Question
What is the minimum energy that must be given to a H atom in ground state so that it can emit an $\text{H}_\gamma$ line in Balmer series. If the angular momentum of the system is conserved, what would be the angular momentum of such $\text{H}_\gamma$ photon?
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Answer

$\text{H}_\gamma$ in Balmer series corresponds to transition n = 5 to n = 2. So, the electron in ground state n = 1 must first be put in state n = 5.
Energy required = E1 - E5 = 13.6 - 0.54 = 13.06eV
If angular momentum is conserved, angular momentun of photon = change in angular momentum of electron = L5 - L2 = 5h - 2h = 3 × 1.06 × 10-34 = 3.18 × 10-34 = 3.18 × 10-38kh m2/s.

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