What is the energy of $He^+$ electron in the first orbit in $eV$?

The time period of revolution of an electron in its ground state orbit in a hydrogen atom is $1.6 \times 10^{-16} \; s$. The frequency of revolution of the electron in its first excited state (in $s^{-1}$) is:

Minimum excitation potential of Bohr's first orbit in hydrogen atom is.....$V$

What is the ratio of the equivalent electric currents produced by the motion of an electron in the first and second orbits of a hydrogen atom?

The energy of a hydrogen atom in the ground state is $-13.6 \, eV$. The energy of the $He^+$ ion in the first excited state will be .... $eV$.

The figure shows a graph between $\ln \left| \frac{A_n}{A_1} \right|$ and $\ln |n|$, where $A_n$ is the area enclosed by the $n^{th}$ orbit in a hydrogen-like atom. The correct curve is