In the first excited state of hydrogen atom, the energy of its electron is -3.4 eV. The radial distance of the electron from the hydrogen nucleus in…

In the first excited state of hydrogen atom, the energy of its electron is $\displaystyle -3.4 \mathrm{eV}$. The radial distance of the electron from the hydrogen nucleus in this case is approximately : (Take $\displaystyle 1 \mathrm{eV}=1.6 \times 10^{-19} \mathrm{~J}, \mathrm{e}=1.6 \times 10^{-19} \mathrm{C}$ and $\displaystyle \frac{1}{4 \pi \varepsilon_0}=9 \times 10^9 \mathrm{~N} \mathrm{~m}^2 / \mathrm{C}^2$ )