The binding energy of an electron in the ground state of a hydrogen atom is $13.6 \ eV$. What is the energy in $eV$ required to remove an electron from the first excited state of a $Li^{++}$ ion?

The energy of an electron in the fourth excited state of the hydrogen atom is

Explain emission lines and absorption lines.

When a hydrogen atom transitions from $n=2$ to $n=1$, it emits a photon. The recoil speed of the atom is $\frac{x}{5} \,m/s$. Find the value of $x$. (Use: mass of hydrogen atom $= 1.6 \times 10^{-27} \,kg$)

The energy of the highest energy photon of the Balmer series of the hydrogen spectrum is close to $... eV$.

Transitions between three energy levels in a particular atom give rise to three spectral lines of wavelengths $\lambda_1, \lambda_2$ and $\lambda_3$. Given that the wavelengths are in increasing order of magnitude,which one of the following equations correctly relates $\lambda_1, \lambda_2$ and $\lambda_3$?