If the wavelength of an electromagnetic radiation is $2000 \ \text{Å}$, what is its energy in ergs?

Find the ionization energy and the wavelength of the photon emitted for a hydrogen atom transition from $n_1 = 2$ to $n_2 = \infty$.

The frequency of radiation absorbed or emitted when transition occurs between two stationary states with energies $E_1$ (lower) and $E_2$ (higher) is given by

When electromagnetic radiation of wavelength $300 \, nm$ falls on the surface of sodium,electrons are emitted with a kinetic energy of $1.68 \times 10^{5} \, J \, mol^{-1}$. What is the minimum energy needed to remove an electron from sodium? What is the maximum wavelength that will cause a photoelectron to be emitted?

When a hydrogen atom (ionization energy $13.6 \ eV$) jumps from the third excited state to the first excited state,the energy of the emitted photon in this process is .............. $eV$.

The wavelength of a particular electron transition for $He^{+}$ is $100 \ nm$. The wavelength (in $\mathring{A}$) of $H$ atom for the same transition is