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

$\frac{x}{x+4}$ is the ratio of energies of photons produced due to the transition of an electron of a hydrogen atom from its $(i)$ third permitted energy level to the second level and $(ii)$ the highest permitted energy level to the second permitted level. The value of $x$ will be.

An electron is in an excited state in a hydrogen-like atom. It has a total energy of $-3.4 \, eV$. If the kinetic energy of the electron is $E$ and its de-Broglie wavelength is $\lambda$,then:

$A$ hydrogen atom initially in the ground level absorbs a photon,which excites it to the $n = 4$ level. Determine the wavelength and frequency of the photon.

If the electron in a hydrogen atom were in the energy level with $n = 3$,how much energy in joule would be required to ionise the atom? (Ionisation energy of $H$-atom is $2.18 \times 10^{-18} \ J$):

According to the Bohr atom model,in which of the following transitions will the frequency be maximum?