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Atoms — Physics STD 12 Science — Question

Gujarat 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 $= E_1 - E_5 = 13.6 - 0.54 = 13.06eV$
If angular momentum is conserved, angular momentun of photon = change in angular momentum of electron $= L_5 - L_2 = 5h - 2h = 3 \times 1.06 \times 10^{-34} = 3.18 \times 10^{-34} = 3.18 \times 10^{-38}kh m^2/s.$

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