Bohr’s atomic theory gave the idea of :

The energy of the first (lowest) Balmer line of the $H$ atom is $x \ J$. The energy (in $J$) of the second Balmer line of the $H$ atom is:

The energy of an electron in the excited hydrogen atom is $-3.4 \ eV$. Then according to Bohr's theory,the angular momentum of the electron in that excited state is ($h=$ Planck's constant).

Which transition in the hydrogen atomic spectrum will have the same wavelength as the transition,$n = 4$ to $n = 2$ of $He^{+}$ spectrum?

Bohr's atomic model explains the spectrum of only $.......$.

The energy (in $eV$) associated with the electron in the $1^{st}$ orbit of $Li^{2+}$ is