Which of the following is a property of the Rydberg constant?

In a hydrogen atom,an electron makes a transition from the $n=4$ to the $n=1$ energy level. The recoil momentum of the $H$ atom will be:

For an electron moving in the $n^{\text{th}}$ Bohr orbit,the de Broglie wavelength of the electron is:

The first four spectral lines in the Lyman series of a $H$ atom are $\lambda = 1218 \, \mathring{A}, 1028 \, \mathring{A}, 974.3 \, \mathring{A}, 951.4 \, \mathring{A}$. If instead of Hydrogen,we consider Deuterium,calculate the shift in the wavelength of these lines.

In the Bohr model of a hydrogen atom,the electrostatic force on the electron depends on the principal quantum number $n$ as:

If an electron jumps from the $1^{st}$ orbital to the $3^{rd}$ orbital,then it will: