Radius of first orbit in H -atom is ' $\mathrm{a}_0$ ' Then, de-Broglie wavelength of electron in the third…
Radius of first orbit in H -atom is ' $\mathrm{a}_0$ ' Then, de-Broglie wavelength of electron in the third orbit is
- $3 \pi \mathrm{a}_0$
- $6 \pi \mathrm{a}_0$
- $9 \pi \mathrm{a}_0$
- $12 \pi \mathrm{a}_0$
Solution
$\begin{aligned} & \text { Radius for } \mathrm{n}^{\text {th }} \text { orbit, } \mathrm{r}_{\mathrm{n}}=\mathrm{a}_0 \times \mathrm{n}^2 \\ & \text { For third orbit, } \\ & \mathrm{r}_3=\mathrm{a}_0 \times 3^2 \\ & \quad=9 \mathrm{a}_0 \\ & \text { Also, } \mathrm{mvr}=\frac{\mathrm{nh}}{2 \pi} \\ & \Rightarrow \quad \mathrm{mv}=\frac{\mathrm{nh}}{2 \pi \mathrm{r}}=\frac{3 \mathrm{~h}}{2 \pi \times 9 \mathrm{a}_0} \\ & \lambda=\frac{\mathrm{h}}{\mathrm{mv}}=\frac{\mathrm{h}}{3 \mathrm{~h}} \times 2 \pi \times 9 \mathrm{a}_0=6 \pi \mathrm{a}_0\end{aligned}$
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Asked in: MHT CET 2024 (10 May Shift 2)
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