The number of spectral lines emitted by atomic hydrogen that is in the $4^{\text{th}}$ energy level is

What is an emission line?

The energy required to excite an electron from the ground state of a hydrogen atom to the first excited state is:

$A$ free electron of $2.6 \, eV$ energy collides with a $H^+$ ion. This results in the formation of a hydrogen atom in the first excited state and a photon is released. Find the frequency of the emitted photon. $(h = 6.6 \times 10^{-34} \, J \cdot s)$

The energy levels of an electron in an atom are shown. Which transition of the electron represents the emission of a photon with the highest energy?

Energy of an electron in $n^{th}$ orbit of hydrogen atom is $\left( {k = \frac{1}{{4\pi {\varepsilon _0}}}} \right)$