CBSE 2024 · Region 5 · Set 1 · Q21 · 2 marks
The earth revolves around the sun in an orbit of radius $\displaystyle 1.5 \times 10^{11} \mathrm{~m}$ with orbital speed $\displaystyle 30 \mathrm{~km} / \mathrm{s}$. Find the quantum number that characterises its revolution using Bohr's model in this case (mass of earth $\displaystyle =6.0 \times 10^{24} \mathrm{~kg}$ ).
Marking-scheme solution
Using Bohr's model:
$\displaystyle m v r=\frac{n h}{2 \pi}$
$\displaystyle n=\frac{2 \pi \times 6.0 \times 10^{24} \times 30 \times 10^{3} \times 1.5 \times 10^{11}}{6.63 \times 10^{-34}}$
$\displaystyle n=2.558 \times 10^{74}$
AtomsDE Broglie’s Explanation of Bohr’s Second Postulate of QuantisationApplyvery_short_answerhard
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CBSE Class 12 Physics past-paper question from the 2024board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.