What is the energy associated with the fourth orbit of a hydrogen atom?
$R_H = 2.18 \times 10^{-18} \ J$

If the shortest wavelength of the Lyman series of the $H$ atom is $x$,then calculate the total energy of the $H$ atom in the first excited state.

$A$ photon of wavelength $3000 \ \mathring{A}$ strikes a metal surface. The work function of the metal is $2.13 \ eV$. What is the kinetic energy of the emitted photoelectron (in $eV$)? $\left(h=6.626 \times 10^{-34} \ J \ s\right)$

On what factors does the magnitude of the velocity of an electron in an orbit depend?

The energy of an electron in the first Bohr orbit of $H$-atom is $-13.6 \ eV$. The possible energy value of an electron in the first excited state of $Li^{2+}$ is (in $eV$)

$A$ $12.75 \ eV$ electron beam is used to bombard gaseous hydrogen at room temperature. The wavelengths emitted belong to which of the following series?