CBSE Class 12 Physics 2013 Paper

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Question : 12
Total: 29
In the ground state of hydrogen atom, its Bohr radius is given as 5.3×10−11m. The atom is excited such that the radius becomes 21.2×10−11m. Find
(i) the value of the principal quantum number and
(ii) the total energy of the atom in this excited state.
Solution:  
(i) r=r0n2
∴ 21.2×10−11‌=5.3×10−11×n2
∴ 4‌=n2
n‌=2
(ii) ‌E‌=−‌
13.6‌eV
n2

‌ Or, ‌‌E‌=−‌
13.6‌eV
4

∴‌E‌=−3.4‌eV
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