The Hitomi satellite recently observed the Lyman alpha emission line ($n=2$ to $n=1$) of hydrogen-like iron ion (atomic number of iron is $26$) from the Perseus galaxy cluster. The wavelength of the line is closest to ............... $\mathring{A}$.

The ratio of the radii of the second and third orbits of an $H$-atom is . . . . . . .

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 $\text{ eV}$)?

The magnetic moment $(m_{orb})$ of a revolving electron around the nucleus varies with the principal quantum number $(n)$ as

The ratio of the kinetic energy to the total energy of an electron in a Bohr orbit is

Energy levels $A, B, C$ of a certain atom correspond to increasing values of energy,i.e.,$E_A < E_B < E_C$. If $\lambda_1, \lambda_2, \lambda_3$ are the wavelengths of radiations corresponding to the transitions $C$ to $B$,$B$ to $A$,and $C$ to $A$ respectively,which of the following statements is correct?