The energy of an electron in the first excited state of an $H$-atom is $-3.4 \ eV$. Its kinetic energy is ........ $eV$.

The recoil speed of a hydrogen atom after it emits a photon in going from $n = 5$ state to $n = 1$ state will be ..... $m/s$.

An electron in a hydrogen atom makes a transition from the $(n+1)^{th}$ orbit to the $n^{th}$ orbit. For large $n$,the wavelength of the emitted radiation is proportional to:

In the Bohr model of the hydrogen atom,the lowest orbit corresponds to:

Energy levels $A$,$B$ and $C$ of a certain atom correspond to increasing values of energy,i.e.,$E_A < E_B < E_C$. If $\lambda_1$,$\lambda_2$,and $\lambda_3$ are the wavelengths of the photons corresponding to the transitions shown in the figure,then:

The ratio of the energies of the hydrogen atom in its first to second excited state is