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

The first excited state of a hydrogen atom is $10.2 \, eV$ above its ground state. The temperature needed to excite hydrogen atoms to the first excited level is

The ratio of energies of photons produced due to the transition of an electron in a hydrogen atom from its $(i)$ $3^{\text{rd}}$ to $2^{\text{nd}}$ energy level and (ii) highest energy level to $3^{\text{rd}}$ level is:

$A$ hydrogen atom makes a transition from $n = 2$ to $n = 1$ and emits a photon. This photon strikes a doubly ionized lithium atom $(Z = 3)$ in an excited state and completely removes the orbiting electron. The least quantum number for the excited state of the ion for this process is:

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

The ionisation energy of a hydrogen atom is $13.6 \, eV$. Following Bohr's theory,the energy corresponding to a transition between the $3^{rd}$ and the $4^{th}$ orbit is.....$eV$.