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Physics · 2022 · 3 marks
CBSE 2022 · Region 2 · Set 1 · Q8
The energy of a hydrogen atom in the first excited state is -3.4 eV. Find: (a) the radius of this orbit. (Take Bohr radius =0.53 ) (b) the angular…
The energy of a hydrogen atom in the first excited state is -$\displaystyle 3.4$ eV. Find :
(a)
the radius of this orbit. (Take Bohr radius $\displaystyle =0.53 \AA$ )
(b)
the angular momentum of the electron in the orbit.
(c)
the kinetic and potential energy of the electron in the orbit.
Marking-scheme solution
(a)
$\displaystyle r=n^{2} r_{0}=(2)^{2} \times 0.53=2.12 \AA$
(b)
$\displaystyle \mathrm{L}=\frac{n h}{2 \pi}=\frac{2 \times 6.63 \times 10^{-34}}{2 \times 3.14}=2 \times 10^{-34} \mathrm{~kg} \mathrm{~m} / \mathrm{s}$
(c)
$\displaystyle \mathrm{K} . \mathrm{E}=+3.4 \mathrm{eV}$ & $\displaystyle \mathrm{P} . \mathrm{E}=-6.8 \mathrm{eV}$
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CBSE Class 12 Physics past-paper question from the 2022 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.