The ratio of the time periods of the revolution of the electrons in the second and third excited states of a hydrogen atom is

Two electrons are moving in orbits of two hydrogen-like atoms with speeds $3 \times 10^5 \ m/s$ and $2.5 \times 10^5 \ m/s$ respectively. If the radii of these orbits are nearly the same, then the possible order of energy states are . . . . . . respectively.

The ground state energy of a hydrogen atom is $-13.6 \text{ eV}$. What is the kinetic energy of the electron in this state (in $\text{ eV}$)?

If $m$ is the mass of an electron,$v$ is its velocity,$r$ is the radius of a stationary circular orbit around a nucleus with charge $Ze$,then from Bohr's first postulate,the kinetic energy of the electron is (where $K = 1 / 4 \pi \epsilon_0$):

If $E$ and $L$ denote the magnitude of total energy and angular momentum of a revolving electron in the $n^{th}$ Bohr orbit, then:

According to Bohr's atomic model,which of the following is $NOT$ a possible energy for a photon emitted by a hydrogen atom (in $;eV$)? (in $eV$)