In Bohr's atomic model,the radius $(r)$ and energy $(E)$ of an orbit $(n)$ are related as:

What is the shortest wavelength in the $Pfund$ series of $He^{+}$ ion?

The energy of an electron in a hydrogen atom in its ground state is $-13.6 \ eV$. The energy of the level corresponding to the quantum number equal to $5$ is ............. $eV$.

Which developments played a role in the formation of Bohr's model of the atom?

The ratio of the velocity of an electron in the second orbit of $He^{+}$ to the third orbit of $B^{4+}$ is:

Consider the following spectral lines for atomic hydrogen:
$A$. First line of Paschen series
$B$. Second line of Balmer series
$C$. Third line of Paschen series
$D$. Fourth line of Bracket series
The correct arrangement of the above lines in ascending order of energy is: