Which of the following is the radius of the first orbit of $He^{+}$ (in $pm$)?

According to Bohr's principle,the relation between principal quantum number $(n)$ and the radius of the orbit $(r)$ is:

If the electron of a hydrogen atom is in the third orbit,it represents its ...... excited state.

The ionisation potential of a hydrogen atom is $-13.6 \ eV$. What will be the energy of the atom corresponding to $n = 2$?

In Bohr's model,the atomic radius of the first orbit is $\gamma$. The radius of the $3^{rd}$ orbit is:

The wavelength of the radiation emitted,when in a hydrogen atom an electron falls from infinity to stationary state $n=1$,would be ............... $nm$ (Rydberg constant $= 1.097 \times 10^7 \ m^{-1}$)