If \(\mathrm{a}_0\) is denoted as the Bohr radius of hydrogen atom, then what is the de-Broglie wavelength…
- \(\frac{8 \pi a_0}{n}\)
- \(\frac{2 a_0}{n \pi}\)
- \(\frac{4 \mathrm{n}}{\pi \mathrm{a}_0}\)
- \(\frac{4 \pi a_0}{n}\)
Solution
According to Bohr, the equation used to calculate the angular momentum of an election in a hydrogen atom is
\(\mathrm{mvr}=\frac{\mathrm{nh}}{2 \mathrm{x}}\)...(i)
\(m \rightarrow\) mass of electron
\(v \rightarrow\) velocity of electron
\(r \rightarrow\) radius of the orbit
\(n \rightarrow\) orbit. number. in. which electron is present.
Given that; election is present in second orbit, \(\mathrm{n}=\mathrm{2}\)
The radius of the second orbit \(r_2=a_0 \times 2^2=4 a_0\)
General formula for radius of \(n^{\text {th }}\) orbit,
\(r_n=a_0 \times n^2\) From (1)
\(m v r=n \frac{h}{2 \pi}\)
\(2 \pi r=n \frac{h}{m v}\)
\(\frac{h}{m v}=\lambda\) (de Broglie relation ship, \(\lambda \rightarrow\) de Broglie Wavelength
So, \(2 \pi r=n \lambda\)
For the electron in the second orbit, \(2 \pi r_2=n \lambda\)
Substitute for \(\mathrm{r}_{\mathrm{2}}\)
\(\begin{aligned}
& 2 \pi \times 4 a_0=n \lambda \\
& 8 \pi a_0=n \lambda \\
& \therefore \lambda=\frac{8 \pi a_0}{n}
\end{aligned}\)
Asked in: JEE Main 2025 (29 Jan Shift 1)