CBSE 2025 · Region 6 · Set 3 · Q27 · 3 marks
In Bohr model of hydrogen atom, an electron is revolving in second orbit. Find the value of :(i)angular momentum of electron,(ii)radius of the orbit, and(iii)kinetic energy of electron. Take radius of first orbit of hydrogen atom as $\displaystyle 0.5 \AA$.
In Bohr model of hydrogen atom, an electron is revolving in second orbit. Find the value of :
(i)
angular momentum of electron,
(ii)
radius of the orbit, and
(iii)
kinetic energy of electron. Take radius of first orbit of hydrogen atom as $\displaystyle 0.5 \AA$.
Marking-scheme solution
Finding the value of-
(i) Angular momentum of electron $\displaystyle 1$
(ii) Radius of the orbit $\displaystyle 1$
(iii) Kinetic energy of electron
(i) \(\displaystyle L=\frac{n h}{2 \pi}\) for \(\displaystyle n=2\)
\[\begin{aligned}
L & =\frac{2 \times 6.63 \times 10^{-34}}{2 \times 3.14} \\
& =2.11 \times 10^{-34} \mathrm{~kg} \mathrm{~m}^{2} \mathrm{~s}^{-1}
\end{aligned}
\]
(ii) \(\displaystyle r_{n}=n^{2} r_{0}\)
\[\begin{aligned}
& r_{2}=4(0.5 \stackrel{0}{\mathrm{~A}}) \\
& r_{2}=2 \stackrel{0}{\mathrm{~A}}
\end{aligned}
\]
(iii) Total energy of electron \(\displaystyle =-\frac{13.6}{n^{2}} \mathrm{eV}\)
\[E=-3.4 \mathrm{eV} \quad(n=2)
\]
\[K=-E
\]
\[K=3.4 \mathrm{eV}
\]
AtomsDE Broglie’s Explanation of Bohr’s Second Postulate of QuantisationApplyshort_answermedium
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CBSE Class 12 Physics past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.