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Question: Answered & Verified by Expert
The ratio of speed of an electron in the ground state in the Bohr's first orbit of hydrogen atom to velocity of light (c) is (h $=$ Planck's constant, $\epsilon_{0}=$ permittivity of free space, $\mathrm{e}=$ charge on electron $)$
PhysicsAtomic PhysicsMHT CETMHT CET 2020 (16 Oct Shift 1)
Options:
  • A $\frac{2 \mathrm{e}^{2} \in_{0}}{\mathbf{h} \mathbf{C}}$
  • B $\frac{2 \in_{0} h c}{e^{2}}$
  • C $\frac{e^{2}}{2 \in_{0} h c}$
  • D $\frac{e^{3}}{2 E_{0} h c}$
Solution:
2799 Upvotes Verified Answer
The correct answer is: $\frac{e^{2}}{2 \in_{0} h c}$
The velocity of electron in Bohr's first orbit is
$$
\begin{aligned}
\mathrm{V} &=\frac{\mathrm{e}^{2}}{2 \varepsilon_{0} \mathrm{~h}} \\
\therefore \quad \frac{\mathrm{V}}{\mathrm{c}} &=\frac{\mathrm{e}^{2}}{2 \varepsilon_{0} \mathrm{hc}}
\end{aligned}
$$

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