The potential energy of an electron in an atom is given by:

If a hydrogen atom is excited by an energy of $8.4 \ eV$,what will be the number of spectral lines emitted?

The wavenumber of the first line $(n_2=3)$ in the Balmer series of hydrogen is $\bar{\nu}_1 \ cm^{-1}$. What is the wavenumber (in $cm^{-1}$) of the second line $(n_2=4)$ in the Balmer series of $He^{+}$?

The radius of stationary state $(n=2)$ of hydrogen atom is $x \ pm$. The radius of stationary state $(n=3)$ of $He^{+}$ ion (in $pm$) is

With increasing principal quantum number,the energy difference between adjacent energy levels in $H$ atom

$1$ mole of photons,each of frequency $2500 \ s^{-1}$,would have approximately a total energy of: